While i can imagine going from Vray to Corona may be a pleasant experience, i can also imagine that going from C4D to 3ds Max may be quite a pain :D
Viewport should not lag when viewing textures... make sure you have all service packs for your 3ds Max version, then up to date graphic drivers, and a good GPU. Viewing textures in viewport is super easy, just click a small checkerboard icon in material editor... it's for showing textures. BUT you need to be in the actual bitmap node, if you use old material editor, or have the bitmap node selected, if you use slate. It will not work in the material... it has to be done in the texture itself.
Absorbtion is based on distance in units. That means at given distance, absorbtion color will have 100% of the effect, at double distance 200%, etc... So you may actually need larger values... Vray's fog parameter does not make any sense... it's some arbitrary multiplier... but multiplier of what? Potatoes? :) In Corona, say you have 1cm thick glass, and you know that absorbtion takes full effect exactly 1cm deep, so you just input 1cm... that's it.