West Highland Way has beautiful views and is a decent hike but is pretty accessible & well known so it tends to be busy year round, falls off the further north you go as the terrain gets rougher. It's about 96 miles too so 7 days is a generous estimate aimed at novices mostly, you can do it in 5 fairly easy.
You can wild camp anywhere in Scotland that's not obviously enclosed (ie farmland in which case you just need to ask permission) except for the Trossachs national park, which the first half of the WHW goes through. There's plenty of bovvies and paid campgrounds along the way though.
May is the beginning of the Scottish midgie season and they're not to be underestimated. Bite isn't that painful honestly, but there care be literal clouds of them and they're small enough to crawl through most fly nets, being bit on every inch of skin constantly will drive you mad fast. I've heard good things about smidge but never used it, the typical remedy is Avon super soft skin cream which will drown them when they land on you. Low lying areas with shade & lots of grass cover are prime midgie areas, dusk/dawn/overcast weather are the times they're out (they don't like the brightness)
When you're in Scotland expect rain and bring at least some not for it, regardless of season, what the weather report says, or what the weather was like an hour ago.Walkhighlands.co.uk
is a great site with all the trails, munros, etc known if you want to browse.