Christopher, thank you for the elucidative, hugely helpful response. And pratterr, I hope you also find this helpful. I know your original post was about solid body vs semi-hollow body vs hollow body. But I think the knowledge about tonewoods is relevant. That I'm not hijacking the thread for my interest.
Yes, I'm talking the SRV/Johnny Winter type stuff. I have a Fender American standard that is Alder body with Fat 50 pick-ups (and maple neck and rosewood FB). I love the tone. But it is still a tad heavy. As you said, Alder is lighter and more consistent than Ash. but I also read that swamp ash is even lighter yet. but I don't know if it is even available any more. I will look into basswood and agathis. I have never heard of agathis!
It's not like I am in any hurry on this; I have lots of time to study and "try a bunch of guitars & ask questions! ". And I'll do this whenever we can get out and go shopping again!
Thank you again, Christopher.
[u]Guitars:[/u] 2014 PRS Santana, 2013 PRS Paul's, 2009 PRS Hollowbody, 1972 Gibson ES-325, 2012 Fender Strat American Standard, 2012 Yamaha Pacifica, Martin M-36, Martin 000-15M, Seagull S6 Classic[br][u]Amps:[/u] Fender Blues Junior III, Boss Eband JS-10, Line 6 POD 500X, Quilter Microblock 45