First of all, I don't personally know any former RCs, now Baptists, who aren't utterly delighted to be out of RCism. They have what the Bible calls the "peace which passes understanding."
And I know lots and lots of Baptists who are former RCs. They are pretty common down here in Texas.
But I do recognize that there are some folks who start out in RCism; who don't know the Lord from Adam; who abandon RCism as unsatisfying; who join Protestant churches (often under pressure from spouses--many of whom were Christians who never should have married unbelievers in the first place); who still don't know the Lord from Adam.
I don't know any such individual personally, since they have never turned up in any Reformed Baptist church with which I have been associated, but I do know enough about bad "inter-faith" marriages to be generally aware of this phenomenon. And I am aware that bad situations like this do tend to get worse.
So, even I can believe that there are cases which seem to fit your scenario, I stand by what I said at the top of this post. Of the many RCs I know, I don't personally know anyone who fits your scenario of RCs becoming Baptists and winding up with less peace as a result. My observations are just the opposite.
Wait a minute: I just thought of an interesting exception. I know an ex-RC who is a Baptist, a single fellow, and who is invariably pretty miserable around his own human family when he visits them ever year over the Christmas holidays. His departure from RCism has created a lot of resentment in that family. And I wouldn't be surprised if his family members misinterpreted his pain.
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In the next place, I believe that there probably are a few ex-Protestants who are more comfortable in RCism. I suspect that these individuals are pretty rare compared to the number of folks who leave RCism. I have not personally met any ex-Protestant RCs, even if I am aware that they exist--for example, here on FR.
In any case, I flatly believe that they are unregenerate. Their experience means nothing to me. They need to read the Bible.