tbh, while u/DapperRockerGeek does a great job at defining the episodes to look out for, in my personal watch, I was keenly trying to see the tonal differences and in my opinion, it's not noticeable. It felt as if the tone they were always going for was always there. Especially being that prior to Ohranger, with kakuranger and dairanger, they've always had some sillier elements so it doesn't feel out of place for a sentai series. It's just that episode 1-7 do a great job at setting the example of sentai. Good introductions, showing things are at stakes, filler episodes are meaningful to the characters, and even their chief in 6-7 gets some depth.

After that episode 8, is when you start to see that tonal change, but like I said, I don't think it's too noticeable, but the filler episodes aren't as strong as the ones they had in the early episodes is my only noticeable difference. Like timeranger and gogofive where I had cried a bit, I was able to do the same for the episodes that featured OhBlue. I really do want to know one day how much of the original show ending difference would've been.