Additionally, the oil leak leaves a roughly 2-3” diameter spot on the floor and it drips on heat exchanger. A very old school reputable shop in Denver diagnosed it as a rocker shaft leak. They installed a few seals around the trouble spot but it didn’t really stop the leaking.

They could be right, but there are a bunch of those seals. And they can be a bit of a pest to get in correctly without slicing them.
Good news on the smoking only happening at cold start up.
Sounds like, to me, that you're in fine shape.
If you are wanting more power, you'd be disappointed with the results of *just* a rebuild.
So, if more power is a goal, then do some digging on ways to get what you'd like, there are many approaches.
I do caution you though, if it involves opening things up, you'll likely do a rebuild service to some degree while you're in there. And thats not like a Chevy 350 from 1970 in terms of pricing. I realize "expensive" is a relative term. If this is your super special splurge car and you drive a 25 yr old Corolla, then, hang on the $$ might shock you. If you're deciding between a new Lucid Air Sooper Dream, or a Taycan private Label, or both...then, well, this is a drop in the bucket LOL

Engines don't loose a bunch of horses just because of some miles. Something needs to be broken or fuel supply out off wack. Seen plenty of engines going really well with lots of miles on the rings and worn valve guides.
Don't expect any measurable gains with a stock rebuild.