As long as your seat height is as far wrong as it is, you cannot know what works for you. My bet is that your hips rock all through your pedaling motion. That is bad for your muscles. It's bad for your most tender skin.

You don't need a different bike to check out stem lengths. All you need is a longer stem and perhaps a Technomic stem to get the height you'll want.. That will force you to bend to each the 'bars, and I hope you bend at your hips, and keep your arms bent at the elbow. .Start with you 'bars as close to level with your saddle as possible. Make your 'bars go forward of the stem so you have to stretch a bit.

You'll solve your butt soreness by taking weight off your butt. You'll open your chest and probably be able breathe better. Your arms will hurt at first, but you'll probably develop core strength, and they'll stop hurting. (I say that because I'm overweight, and my upper body is weak, but my core gets strong enough by the end of the season if I focus on decent form.) You'll find riding easier and more enjoyable.

Some time conventional wisdom is conventional because it works well. Try it - it may work for you.