Main Salmon? Mmmmmm...... One of the finest river trips out there. Late June/early July? Water should be coming down, but it's better there, more crashing waves, etc. At 7ft (Corn Creek), which equals about 26-28K cfs if I recall (check the USFS website and there is a good sign at Corn Creek that spells it all out, what feet it is, how many cfs that is, etc.) most runs were straightfoward BUT it is wise not to take on the meat of everything you see. There are BIG laterals that WILL flip a boat, etc. But overall it is straightfoward.
I HIGHLY RECOMMEND Eric Newell's guide: Idaho's Salmon River, a river runner's guide to running the Main Salmon River, Idaho's Salmon River by Eric & Allison Newell
Has terrific, simple explanations of the rapids along with easy to understand "sand drawings" (actually pencil) showing major obstacles and good lines through all the important rapids.
Check for updates, because Salmon Falls is now underwater and has been replaced by a new rapid 1/4 below at Black Creek.
Other than that, much depends on water level. At 7ft the very fist rapid, Killum, had a Crystal size hole on the left, but a highway of water went by it so it was no problem. The Salmon and the Snake are both like that. Very big water, but room to move across or around. The sneakiest thing about those rivers are the laterals in the midst of wavetrains around bends or in rapids that would normally be piece of cake.