(Some summary of ring & cylinder adjustments based on other notes)
A new platen in many cases will help to solve some of the proximal problem, but you'll still have heavy wear on your paper/ribbon and your new platen over time as a result. The first adjustments a pro typewriter repair person would make after installing a new platen would be to check the ring & cylinder, on feet, and motion which can all be subtly out of alignment with a new platen.
Pretty much every typewriter in modern era has adjustment points for this. All three of the machines you name definitely do. You'll find some of the basics and adjustment points for several machines described at https://typewriterdatabase.com/1945-AMES-OAMI-MechanicalTrainingMan.v1-ringcylinder.manual. If you look at the manuals for specific machines that Ted Munk has collected at the typewriterdatabase.com, you'll find how/where to make those adjustments. Several on Polt's website describe the adjustment as well: https://site.xavier.edu/polt/typewriters/tw-manuals.html#servicemanuals
Some sources may describe the adjustment as hammer and anvil as opposed to ring and cylinder.
You're also likely to find YouTube videos on them as well (I'd check Phoenix Typewriter's channel first, though I do recall he mislabeled one once on a S-C Skyriter which was really an on feet/motion adjustment.) Duane's also got a really subtle and uncommon adjustment on a Royal QDL here: https://www.youtube.com/watch?v=KOET0i3DsR8
Gerren gives an adjustment nod for the Olympia SM series here: https://youtube.com/watch?v=2jnC6ODB834&t=670s And here's a blogpost about the adjustment points for an Olympia SF: https://ber10thal.com/blog/repairing-a-1961-olympia-sf/
Related blogposts from Munk for a Brother JP-1:
- https://munk.org/typecast/2022/01/23/adjusting-ring-cylinder-on-a-brother-jp-1/
- https://munk.org/typecast/2013/07/30/typewriter-repair-101-adjusting-vertical-typeface-alignment-segmentbasket-shift-typewriters/
Hopefully your machines and hardware appreciate the finer adjustments and wear better over time as a result.
Happy typing!