Is there a bolt material that would be better matched perhaps?

Don't think so. Just is what it is. Its not a problem as long as you employ the couple things mentioned.

I have never had any issue removing these. I never use a tq wrench on something like this. It is so non-critical and low tq I dont even consider it. Have never put anti-seize on them either. Just dont over tq them ;) You literally can tighten them with your hand on the head of a 3/8 drive wratchet (not using the handle) and they are fine with just a good snug up that way. But if you are concerned with the corrosion then yes, just add a dab of regular old anti-seize.

I had issues in past with just hand tightening with an actual Allen wrench, not even a socket.

I see, well I'll just go to ace hardware and buy the bolts and anti seize. Kind of getting annoyed at looking at the valve cover without spark plug cove since few months ago when I did the coils and spark plugs.

6mm x 1.0 thread pitch, and 18mm long