My Mini-Thirty eats Wolf ammo as well as any other. No, the varnish has not to this day caused any problems for me. Roughly 1000-1200 rounds of Wolf through it. Clean every other time at the range. "How easy is it to clean the entire rifle after shooting corrosive ammo?"? Simple - don't shoot corrosive ammo. The Wolf is not corrosive. Cleaning in general is exactly the same process as with a Mini-14.
Groupings on my -Thirty are about 2-2.25" at 100yds with a Black Warrior Double-Muzzle Brake and a glass-bedding job done by me. I think they started out at 4" groupings. Great gun. Never a jam, except with lousy after-market hi-cap mags. Ruger 5-round mags - never a single problem.
The main thing to consider is buying hi-cap magazines. The hi-caps for Mini-14 are easier to locate, and GOOD Mini-14 mags are hard to find. Ruger Brand hi-caps for Mini-14 are EXPENSIVE.
Ruger Brand mags for the -Thirty only go up to 5-round! Aftermarket GOOD hi-caps for the -Thirty are harder to find than for the Mini-14. Four-Four mags is your best shop for 10-rounder -Thirty mags.