Randomizer

Roll a new seed from given settings

Mode is the general "Shape" of the course and its distribution of pars.
Sources
Some Mario Open courses are the same or similar to NES Open courses. You probably want to keep this turned off.
An "Expert Hole" is any hole from Mario Open that's been determined to play harder relative to par than any hole from NES Open. There are around 20 such holes.
Each hole in the course will be rolled for all transforms, so no specific count is guaranteed.
Club Restrictions

These settings place restrictions on which or how many clubs players may use. Most of the time you'll want to leave all of these fields at their default values.

Banned Clubs
Locked Bag
Checking any of these checkboxes will require all players to use exactly the checked clubs, as well as a putter. You will not have access to any unchecked clubs. The limit is 14 clubs, plus the putter.