blanks are probably the most popular for any ergo boards, with some layouts being very different than standard 104's key placement (moving punctuation, brackets, modifiers, etc...). you can find cheap blank sets all over the place
varying profile depending on row - OEM, DCS, SA, Cherry, MDA, KAT, etc...
uniform profile - DSA, XDA, etc...
another option is to do a single profile of a normally varied profile, like all SA row 3 or similar with another profile.
just about any profile should work. only issue i can think of was some of the SA profile keycaps, one row, because of the profile was pretty close to the next row and had a possibility of rubbing.
uniform profile is another option if you want legends on your keycaps, uniform profile is the easiest to get the legend to match the key without being out of profile. again, because the keymaps sometimes don't match what is readily available in standard 104/TKL sets.