Shawn, this is a tricky one...
Variation #1
Verse 18 is simple. All are made rightous. Because the Bible doesn't contradict the many in verse 19 simply means all.
Variation #2
Verse 18 claims all people were made sinners. Jesus wasn't a sinner. So all is not 100%. It's believers only
Verse 19 just says there are many believers.
Variation #3
Both verses define groups. The groups don't change within the verse. So if all a doomed all are saved. If some are doomed then some are saved. Those that were not doomed don't need to be saved.
Knoch's commentary.
18 The parallel here is perfect. Adam's one offense is counteracted by Christ's one just award. The act of Adam actually affects all mankind. So Christ's work, eventually, must also actually justify all mankind. This cannot be during the eons, hence will not be fully accomplished until after the eons are past, when all are made alive in Christ (1Cor 15:22). If Adam's offense only gave each one an opportunity to sin, so that some become sinners and others not, then we might say that Christ's work brings justification to all subject to their acceptance. But we must acknowledge that man has no choice in becoming a sinner, thus also will it be through the work of Christ. Both are actual and universal.
19 The contrast here is between one and many, not between the many and the all of the previous statement. The many here are the all of verse eighteen.
The verses are about contrast. One person has a negative impact on many. But one person also has a positive impact on many.
Because of it's clear/widely accepted that Adam sinned and automatically everyone else was doomed, it's also reaonbly to assume the contrast implied here is that because of Jesus' sinlessness automatically every is saved.
The KJV translation doesn't seem accurate to me. First a few different translations:
18 Hence then, as through one fault, [the sentence was] unto all men unto condemnation, so, also, through one recovery of righteousness, [the decree of favour] is unto all men for righteous acquittal unto life;
18 So, then, as through one offence to all men it is to condemnation, so also through one
declaration of `Righteous' it is to all men to justification of life;
18 So then, as through an offense of one man was for condemnation for all men, so also through a righteousness of one man was
for justification of life for all men.
18 So then as through one trespass the judgment came unto all men to condemnation; even so through one act of righteousness the free gift came unto all men to justification of life.
18 So then, as the effect of one act of wrongdoing was that punishment came on all men, even so the effect of one act of righteousness was righteousness of life for all men.
18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men to justification of life.
18 Therefore, as through one man's offense judgment came to all men, resulting in condemnation, even so through one Man's righteous act the free gift came to all men, resulting in justification of life.
18 Therefore, just as through the offense of one, all men fell under condemnation, so also through the justice of one, all men fall under justification unto life.
18 so then as it was by one offence towards all men to condemnation, so by one righteousness towards all men for justification of life.
18 Therefore, as by the offence of one, unto all men to condemnation; so also by the justice of one, unto all men to justification of life.
18 Thus as through one downfall all humanity is unto condemnation; even thus through one justification all humanity is unto justification of life.
18 Therefore as by the offence of through one judgment came upon downfall to all men humanity is to condemnation; even so thus by the righteousness of through one the
free gift justification came upon all men to all humanity is unto justification of life.
18 So then as through one trespass the judgment came unto all men to condemnation; even so through one act of righteousness the free gift came unto all men to justification of life.
18 So then as through one trespass, all men were condemned; even so through one act of righteousness, all men were justified to life.
18 Therefore, as by the offense of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.
18 Therefore, in the same manner that by the iniquity of one [guilt came] upon all men unto condemnation, even so by the righteousness of one,
[grace came] upon all men unto justification of life.
18 Consequently, just as condemnation for all people came through one transgression, so too through the one righteous act came righteousness leading to life for all people.
18 So then as through one trespass, all men were condemned; even so through one act of righteousness, all men were justified to life.
18 So then as through one trespass, all men were condemned; even so through one act of righteousness, all men were justified to life.
18 As then through one trespass all men have come under condemnation, so through one act of righteousness all obtain the gift of righteousness unto life.
18 The result of one trespass was condemnation for all men. The result of righteousness was justification acquittal, which brings life for all men.
18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men to justification of life.
18 Therefore as by the fall of one for all men to condemnation; so also by the justification of one for all men to justification of life.
18 So then as through one trespass, all men were condemned; even so through one act of righteousness, all men were justified to life.
18 Therefore, as by the offense of one, judgment came upon all men to condemnation, even so by the righteousness of one the free gift came upon all men to justification of life.
Many translations show that life/justification was declared/forced upon.
That aligns perfectly with the following verse: Romans 4:5 But to the one who does not work, but believes in the one who declares the ungodly righteous ...
God wasn't begging for someone to accept it. He simply declared it. Even, especially, on the ungodly. If verse 5 declared ungodly rightous it would be silly to assume verses 18 and 19 are about believers only.
The Greek in verse requires a lot of 'adding' to translate it to English.
Rom 5 [KJVCNT]
18 Therefore as by the offense of one judgment came upon all men to condemnation; even so by the righteousness of one
the free gift came upon all men
unto justification of life.
The red words are both translated from the
same Greek word.
εἰς
eis
Thayer Definition:
1) into, unto, to, towards, for, among
Part of Speech: preposition
A Related Word by Thayer's/Strong's Number: a primary preposition
Citing in TDNT: 2:420, 211
My

conclusion.
Whatever the number of doomed people, those very same doomed people are made/declared rightous. No conditions of any kind. Love your enemy.