There's been some discussions and TLs about this scenario in the past (I would be in trouble if I had to find them, though), and the answer is, to my knowledge and personal opinion - who the hell knows?
Lithuanian history after 1385 was so universally defined by the Union of Krewo that there are very few things from that point onward which we could say would also happen in a no Krewo world. But here are some of my thoughts:
1. Jogaila would not leave his country for Poland and thus would not leave a vacant throne back in Lithuania. This would have severe impact on the ATL equivalent of the Lithuanian Civil War of 1388-1392, though I would not say it would completely butterfly it away, as Jogaila's style of rule was far from popular among the members of the House of Gediminas. Still, with Jogaila in control and not his incompetent viceroy Skirgaila, Vytautas's victory over his cousin is very unlikely. If he gets lucky somehow (say, the Teutonic Knights decide to help him more meaningfully in TTL, for whatever reason), then he could possibly pull off a restoration of pre-Jogaila dualism, with him as the second-in-command, but it's just as likely that he ends up as a slightly more ambitious version of Švitrigaila and dualism in Lithuania dies.
2. Christianization of Lithuania is still very likely to happen, but without Jadwiga and the easy conversion card it brought to the table, conversion would be more messy and even less smooth than it was in OTL. However, without as much direct Polish influence and thus subsequent Polonization, I believe it would be for the better. When Lithuania converts depends on how the situation and chances to Christianize develop in TTL. A conversion to Orthodoxy is slightly more likely than it was in OTL, but not by much - the main reasons for why Lithuania did not accept Orthodoxy, this being fear of continued Teutonic raids and a feeling of superiority over their Orthodox subjects, would remain.
3. Relations with the Rus' principalities and Moscow are, once again, somewhat of a mystery. We don't know much about Jogaila's plans for the east, seeing as he only ruled Lithuania directly for a few years and most of that rule was a continuous civil war, but we do know that unlike Vytautas, he was an opponent of Tokhtamysh and ally of Mamai during the war with the Blue Horde, which would make relations with the Golden Horde very interesting if the Tokhtamysh-Timur war happens like in OTL. However, in general, I don't think Jogaila's Eastern policy would be too different from that of Vytautas - both of them were influenced by the plans and policies of their predecessor Algirdas.