With the 101+ skill caps I don't think there are any hard caps to anything, it's all decided by character skill.
This is my idea of how the lockpick system could work as I don't know the full details of how the 1st gen Fallouts were.
So with 100 in Lockpick you'll be decent enough at lockpicking but you'll break several picks and might even break the lock if going for a stronger lock while at 300 all locks will be opened far more easily. (this removes the minigame though.)
So it's not about "At X you can do Y" it's more about "At X you're this good at doing Y".
So take an easy lock, it requires 1 to 100 in Lockpick skill.
At 1 to 100 it's all decided by % of chance to pick the lock.
At 20 Lockpick you'll have 20% chance to pick it.
Once you go above 101+ it's 100% chance to pick the lock.
Now a medium lock requires 50 to 150.
If you have 40 in lockpick your chance at picking the lock is 1% (Always 1% on all locks).
So when at 100 you have 50% chance to pick the lock.
The amount of times you can try on a lock depends on what lock durability it has and your skill.
A character with 7 lockpick will most likely break a very hard lock on the first try.
So the lower the skill you have the more damage you inflict on the lock if you fail to pick it.
While the higher the skill you have the less damage you inflict on the lock if you fail to pick it.
Same thing for just about everything else.
A stimpack requires 80 to 160 Medicine to craft.
If at 80 then the stimpack will be low quality and not heal as much while one at 160 will be perfect quality and heal more than standard stimpacks. (still not as much as super stimpacks.)
At at 160+ you get a % to create two stimpacks instead of one.
So at 300 you might just craft 3 quality stimpacks for the price of one.
You can still craft a stimpack at 30 in Medicine but you only have 5% chance to craft one and it will be a crap quality stimpack too.
That's the way I figured a 300 skill cap could work.
Still, it's not a requirement to bring it up to 300.
300 costs a lot of points.
So stopping at 200 or 150 won't harm your character too much.
You'll be really good in that skill but you will still have the occasional fail moment.
It's just that 300 will mean your character is an absolute expert in that area and will be successful no matter what he/she does.
The older Fallouts' 300 cap was very unnecessary as it didn't really do anything and was by far too hard to get to.
Changing it to this could increase the 300 mark's potency.
Why we consider the older Fallouts skill system to be superior though is that Tag skills are more important with the "1:2 2:2 3:2 ratio" while untagged skills go by "1:1 2:1 3:1 ratio."
It means that we won't get maxed characters as it will require a [censored]load of skill points to achieve this.
Tagged skill will be easier to reach 200 with while untagged skills are best to leave at 100.
It will allow for greater specialization and smarter skill point allocation.
Aaaanyway.
Fallout 1 lvl cap 21. skill cap 200
Fallout 2 lvl cap 99. skill cap 300
And I mostly reache around 150 in all of my three tagged skills and then 100 in one or two others.