I think being hot is generally better when you enter the playoffs, but I'm not sure historically that matters. Last year the final 4 teams over their last 20 games were a mixed bag. The Heat were 12-8 which is worse than the overall season. The C's were 15-5 or better. Out west the Warriors were 10-10 (and going back further were 12-15 in their last 27) while the Mavs were 15-5 (better). So 2 of the final 4 teams entered the playoffs performing worse than their overall season for over a month, including the eventual champion.
Err. The Warriors circumstances are pretty unique, since Curry missed the last 12 regular season games, and played 13 minutes immediately before going out. Curry played four healthy games out of the Warriors' last 18. The Dubs won all four of those games, and went 6 - 8 in the other four. Notably, even without Curry, they won their five games leading into the playoffs.
Also notable: Draymond missed 32 of his last 52 games, Klay missed 52 on the season, and Porter missed 8 of 17 games to end the season.
The year before, the Bucks finished the year 14-8 (and 17-12). The Suns finished at 14-6, which was actually off their pace and the Suns played the Clippers that actually limped into the playoffs at 4-6 in their last 10. The Hawks were about the same.
Going back further (not the bubble year), the champion Raptors entered the playoffs having won 7 of 8, but over their last 20 were 13-7. The Warriors were 14-7 in their prior 21 games that year, also off their regular season pace. The Bucks were 12-8 (worse) and the Blazers were 15-5 (better). So 3 of the 4 teams were worse down the stretch than as the season as a whole.
Year before Cavs 14-7, Warriors 7-9 (11-9 if you go back 20), Celtics were 13-7, and the Rockets were 16-4. So the Cavs and Rockets were better, the Warriors (the champion) and Celtics were worse.
The most important thing for teams entering the playoffs, is to enter healthy and rested. It really doesn't matter if they win or lose, they just need to be ready to go when the playoffs start.
The season is long, there are ebbs and flows, but as the season goes Boston has the 2nd best record in the league and many of the advanced metrics also have them as a top 2 team. If they are healthy for the playoffs, that is what matters. As I've said all year, I think Milwaukee is the only team in the East that can beat Boston in the playoffs, and I still maintain that. Nothing I've seen yields a different conclusion for me.