You've probably already read through the dev blog they put out on the Season 2 loot changes, but if you haven't that's the place to start. (tl;dr- run +7 or higher and you get a chance at it)

It sounds like you're asking what the chance of a level 100 item is versus something lower, given that you've already met the criteria for them dropping and that you're level 100. The answer is: "...the distribution is a flat random from all the available levels (max your level)". This is from a dev, so it's probably accurate.

Hope that helps!

need to do 7+ level missions

Season 2 is not active on consoles yet if I'm not mistaken (we're still at inferno).

On ps4 the tarot cards are still set to a specific level (i.e.: 70, 80 and 90).

Will you have to play with a seasonal character for this to be in effect or is this effective in non-seasonal playthroughs as well?

The changes to Tarot and item level should affect non-seasonal characters, too, but only after the Season 2 patch has been ported to console.