What's the point of even getting the license from WOTC if you're not going to make a game with D&D rules?
Following my own advice and starting this with "Please do both, both is just better than either alone", I do have to point out that RTwP is going to ruin it for you if you're concerned about following the core rules. D&D is a turn based game. The moment you switch to RTwP, you have to massively change a whole slew of things to make the game work. Its the core mechanic of combat, you change it, you have to rewrite the whole thing from the ground up. I love the BG series, but they play absolutely nothing like a tabletop in any measurable way. Most of what's good/fun/rewarding about strategic thought and party planning in tabletops is utterly absent in RTwP games, as there's no feasible way to pull it off due to the overlapping chaos of actions.
Take hit rates for example, if its RTwP they're going to get adjusted away from the core ruleset, there's no two ways about that. One of the things hit rates in a TB system assume is enemy actions being split up by friendly actions. Your ranger gets hit by 3 of the 6 enemies you are facing, but then turn 4 your Cleric comes up and can throw out a heal, so you're doing okay. In RTwP, all 6 enemies act at the same time. If all 6 hit your ranger, boom, ranger dead, no opportunity for counterplay of any kind. Time to save scum or write off the Ranger, all while your Cleric has a full complement of healing spells available you simply weren't given the opportunity to use. How do you offset this in RTwP? You bottom out enemy hit rates to spread the damage, and up Player hit rates so they can chew through multiple enemies faster before a stroke of bad luck still causes those 6 simultaneous hits.
Pathfinder Kingmaker is a rather depressing direct example of this exact thing. I love, love, loooooooove the Pathfinder ruleset with all my heart. I was so excited to hear a PC game based on it was being released. Then they did it RTwP, no TB option. The result? A game with a veneer of Pathfinder lore and gameplay that is literally NOTHING like Pathfinder, at all, in any way. It was hideously disappointing to say the least. To be fair, it might have been a fun game if I hadn't wanted it to be Pathfinder, but because I bought Pathfinder Kingmaker hoping for a Pathfinder game, and got a generic RTwP "select all and autoattack" snoozefest, it was just a huge letdown.
Anyway, I digress, I really just wanted to say, if you want a game that keeps the actual D&D ruleset, I would suggest advocating hard for it having both RTwP and TB, because the TB option makes it much more likely they'll actually use the mechanics of the source material.
