I really hate the word toxic. But, no I don't think they have a good, loving relationship. Ross had a crush on her in high school. That's fine. They meet up again years later and he says something about going out, she agrees, but it never happens. Again, fine. But, then he just moons over her for a whole year, which, IMO, is a little creepy. She finds out that he likes her (really, how did none of the girls notice this all year?), and decides maybe she'd like to date him. OK. But, then he comes home from China with a girlfriend. The two reasonable things for Rachel to do is to a: drop it. After all, she just interacted with him for a whole year without feeling the need to date him. Or B, get him alone and tell him how she feels. But, instead she passively aggressive tries to throw little chinks into their relationship.
Ross finds out Rachel likes him and decides to decide who to date by making a pro/con list. I don't have the problem with this some have. Although, that should have just told him to date Rachel, because he clearly wasn't all that in love with Julie if he needed a list after dating a few months. But, anyway, she found out about it, didn't like it and decided not to date him. Again, fine. You can date or not date whomever you choose for whatever reason. But, then Ross got all possessive. Not cool.
Then they date for a year and I'm not even going to touch on the break or not a break thing and just say they broke up for some reason. They then get past their animosity and start being friends and then Rachel wants him every time he has another girlfriend.
The whole thing is just stupid and they needed to move to different states eons ago.