Technically infusion is claiming that you can infuse up to 350. So it's looking like that might be the end cap when the hard raid is out. Additionally, at least one exotic quest I have requires the raid, so there may be more. Nightfall has a 230 and 300 recommended power variant, with the 300 being called prestige. The two affixes currently are Prism, which is essentially a rotating burn, moving at a rate of a switch every 20 seconds. It only powers up the three elements, and does not affect enemy or kinetic damage. The other is that the Nightfall is on a 10 minute timer, but now if you go over time the mission fails. Killing enemies will add time, with two seconds added for red bars and up to seven for yellows.
Also, don't save engrams. An engram is fixed to your light at the time of drop, not decrypt, so you can't hang on to an exotic engram until almost at max light for that little push like D1.