I have no idea about whether or not your wife is doing anything inappropriate, but i will say that i have a lot of matching bra and panty sets that i don't really consider lingerie and i do wear them for myself, not just for my boyfriend. I also have true lingerie that he's never seen because I've bought it but just didn't end up feeling confident enough to wear it or am just saving it. I also have some borderline sexy matching PJ sets that are lingerie-adjacent, and I'll wear them on a business trip just because it feels like fun and fancy and adult to lounge in a hotel room alone in something sexy. I've never cheated but your exact situation could have feasibly happened to me.

Not saying there's nothing nefarious going on, but her explanation about the underwear would track for me. Sounds like there's more that's setting off alarms for you though.

Not a lot of advice but i live in an alpha building which they bought mid lease. They've done nothing but make things worse and increase rent. If you call the maintenance people there's like a 50% chance they'll end up screaming and swearing at you on the phone. It took them 6 months to fix my leaky faucet which is nothing compared to what my neighbors have gone through.

Our neighbors all have a group chat for kind of teaming up to deal with issues that come up like hot water or heat being out (like a twice per month occurrence during winter), their maintenance people leaving doors propped open resulting in packages getting stolen, letting brokers into our units illegally with no notice, etc. It doesn't always result in action but having a team of us to call and nag or give each other heads up about their terrible management has made me feel better. Might be worth setting something like that up if you plan to stick around.