Well, you can take V4 to V8 in steps, if one product gets it to V7 you can then move those transferred poses to V8. The products all work on both male and female. You will need to do some tweaking, but you need to do that to poses even if they are in the same class depending on the morphs you are using - normal M7 poses don't work for George for example without some modifications to allow for his, um, 'unique' proportions.

Also the hands are always a problem, there is another product that fixes the hand positions, none of those products work correctly on hands that I know of. The one that does hand fixes between V4/M4 and G1, G2 is https://www.daz3d.com/handy-dandy

Any poses that have multiple figures involved and touching will also need tweaking. Again, those usually do out of the box if the figures are not default size even when not transferred.