Galling can be an issue if the machining is really rough, but in most cases it's entirely preventable with good lubrication, as you suggest, and shouldn't be a problem with decently made guns. Especially if the gun has a good hard anodizing, you should be fine. I also wouldn't worry about galvanic corrosion. Only exception to that would be a graphite-based lubricant, which could be a problem in damp places or sweaty EDC, as graphite is known to enhance galvanic corrosion. So stay away from anything with graphite in it, and stay away from light oils. Go with a heavy oil, or even better a good lightweight grease, like TW-25b or one of the cherrybalmz greases. Not a heavy grease though, they aren't good in semi-autos. A heavier oil or light grease.
You should be good to go with the frame in general, I wouldn't worry about cracking an aluminum frame these days, esp in 9mm. If it's something you're really concerned about, get a Sprinco Recoil Managment Guide Rod - they absorb a lot of the shock of the slide-on-frame impact with a heavy secondary recoil spring built into the rear of the rod, that gets engaged just before the slide hits the frame. Unlike the ShokBuffs, the Sprinco system actually captures that energy and uses it to propel the slide forward again, so it's win-win. I put one in a .40 S&W Sig 229 about 15 years ago, and it's been the softest shooting .40 I've ever fired. Feels closer to hotter 9mm than .40. I'd love to put one in my 9mm DWX Compact, but they don't make them yet.