For the basics, learn to fly the Yak-1. It might be the most reasonable to learn and fly, take off with - and has capability...then I wouldn't worry about mixture starting out
What stick are you using. Is your Trim and RPM on there? Do you use a throttle? Yes, you definitely need to adjust your RPM and Throttle in tandem without overheating. Very fun to learn once you get the hang of it. ( like driving a car in 3rd gear on the freeway if not set up) ...also your trim needs to be adjusted on the fly - (like having your foot on the brake on freeway)
get those simple mechanisms down and you'll be fast...definitely play with the trim with the hud on to see whats happening.
dont get too upset. Ive probably flown 1000 hours since 1946 ..and will still manage burn up a p40 engine by not paying enough attention..