Are there any implications about review paper acceptance if the proposal has been accepted?
My experience is that review articles undergo peer review like any other article. So if you write a review on underwater basket weaving, it'll be sent to experts in underwater basket weaving, who might say things like "X group did a lot of work on the materials that give the best results, and you didn't mention their work at all". If the editors decide based on the reviews that you don't actually understand underwater basket weaving enough to be able to write a review, then it might lead to a rejection.

If you make a good-faith attempt to cover the field + address review comments though though, the chances of acceptance should be pretty good. After all, they did accept the proposal, which means they think a review article is appropriate + you're qualified to write a review.