Tay-Sachs is prevalent among certain communities that are descended from Eastern European (Ashkenazim) Jews.
Though the Orthodox are complex in certain ways.
The Satmar a very insular, but the Lubavitcher are very progressive in some ways.
I suppose both have problems with intermarriage, though to a much lesser degree.
After all, I don't think that you can convert into being a Mennonite or Amish, while Reformed and Conservative Jews can-theoretically-convert to Orthodoxy if they so desire.
You can certainly convert to these groups, but there is a big cost.
There are several types of Amish. The Old Order Amish are the ones you commonly think of: buggies, etc. The Beachy Amish, however, drive cars and are a little more "out there" outside their own community. You'd stand a better chance being accepted into (and being part of) a Beachy church.
There are Mennonites (called Wenger Mennonites) who drive buggies similar to the Amish. There are Mennos on the other end of the spectrum who wear normal modern clothing, women with cut hair. They believe much more in the spirit of Menno Simons and the Anabaptist path than the letter of the law (which in most cases was man-made to begin with). You would have no problem hooking up with a Lancaster Conference Mennonite church. Beware that some are getting rather liberal, accepting homosexuality, but for the most part they are still conservative.