Potential 360 build couple of questions

no.
it means you use the existing roller lifters for another hyd roller cam other than stock, and another plus besides the the hyd roller cam...the LA heads.

solid roller lifters are all link bar style and will work in a LA or mag with maybe minor clearancing of the valley.

see thats thing people keep forgetting while pondering the better of the two, once the cam changes to a solid roller....no advantage.
they both will take the same 'after market' solid roller parts.