pre c.1790 Church of England (Espiscopalian), post 1800 about 50% Methodist;
Presbyterians were very rare being most of Scots origin; Roman catholic were also equally rare being mostly Irish;
post 1850 things changed a little but Presbyterian generally still Scots

Use of 2 initials pre c.1870's rare among manx - very much an American custom (taken I think from German settlers)