I can't see any reason for 5 suits barring a month long trip. Two or three would be the absolute max, generally two.

I would never check a garment bag, they are not built to stand up to that abuse, especially if you have expensive suits. Get a hard shell if you want to check anything (I would recommend not). If you get a bag lost, you have no suits unless you are wearing one.

If you want a great garment bag, the Patagonia MLC Burrito was fantastic. It's not in production but can be found on eBay and such. Great construction, thoughtful pocket layout. Great paired with some like the Bihn Pilot for you electronics.