I don't have a tonneau cover and can't get one soon due to being in Germany and shipping costl/restrictions are prohibitive.

What strap size (if any) I should be using? I know only about the thick straps used commercially and in the military, not sure if they will fit the holes or even where to get them. Any suggestions so my suitcases and general luggage doesn't fly off when I decide to utilize the bed? (this is my first truck so I am new to all of this)

 

Try something like this: https://www.etrailer.com/dept-pg-Cargo_Nets.aspx

I got this cover and it's been great. Available from many sources. https://www.etrailer.com/Tonneau-Cov...leid=202128448

I think it would be cheaper to get the cover as your first purchase.

 

I can't see things like suitcases/luggage flying out of the pick-up bed (unless the tailgate is left down & it slides out) I've never had a problem !!
If something is left open & it is light enough (open box etc. )air could pocket & it could come out that way ?? But you do have the Autobon
Try that cargo netting maybe off Amazon ??