Trusses are definitely not designed for storage but they aren't toothpicks either. I'm sure most trusses are engineered to carry a 2nd layer of roof as many will do an overlay to save money.
I still think the insulation will hamper your ability to use the space for much storage. However, if you are determined, you could install some catwalks and slide empty plastic containers down each run. I'd insulate and install these catwalks (really 'crawl-walks') elevated to float over the insulation. You would do this by addling lateral blocking to place the walks.
I have a hook on the end of a paint extension pole. I can poke my head and shoulders up inside the attic and pull things to me. When I put them back I just line them up and push them down the walk. No need to actually be up there yourself.
There was a comment about ringing the garage with shelves about the 6 foot line, or just low enough to put containers all along the upper walls. This is the best system. Each container can be labeled and you can see what is what from the ground. A lot of the weight is carried by the wall, and if braced from below, all the weight is on the wall. Better yet, your storage items won't be at zero degrees.....ever.
Edit: I just realized the I was repeating what @Innovate1 has already said about elevating any 'walks'.