Re Springers, I'd make two comments.
1) The term "Springer" tends to get used to describe any rough old boat of unknown builder, so the OP may well encounter supposed 'Springers' that are actually flat bottomed. But this will probably be because were not built by Springer and they have been mis-attributed.
2) V bottomed boats such as Springers can be a right PITA when it comes to internal fitting out. To get more headroom the floor height is likely to be low in such a way the slope of the hull is higher than the floor at the sides, and hidden by built-in seats, kitchen cupboards, bed etc. This can make it really difficult to fit say, a modern under-counter fridge or a free-standing cooker as they rely on a flat floor all the way back.