Koopowitz covered this in several articles. Any species or hybrid that a mature, 3 growth plant will bloom in a 3 inch pot and total height is less than 9 inches and overall leaf span less than 8 inches, could be considered compact. As a side note; in my mind, true mini doesn't start until you are at or under 4 inches - this Paphs simply don't do well, so I think the 8 to 9 inches and fit in a 3 inch pot is an acceptable rule. At this size a teacup could be used as a pot or cachepot. Easy to grow is relative, I find parvi's easy and callosum types difficult - because I grow fairly cool. So ease of growth should be ignored as far as defining the type.
My picks for the list would be
armeniacum
micranthum
concolor (not all races, there are some larger growers too)
niveum
godefroyae
thaiianum - have never seen it live, so this is from what I've read
appletonianum - some clones are more compact than others I have a small clone labeled as wolterianum that fits the bill.
barbigerum
helenae,
henryanum
hermanii
charlesworthii & fairrieanum & spicerianum all can get too big for the mini category, but there are some clones that are more compact than others.
tranlinianum
primulinum
wilhelminiae - some clones are smaller than others.
fowliei of course - smallest of the barbatum-callosum group
purpuratum & barbatum, some clones will bloom rather compact.
wardii - you can usually keep a 2 growth plant blooming in a 3 inch pot, eventually they get big.
Paph lynniae is too big, but it is the smallest of the lowii group. Almost on the list.
Paph philippinense, there is a dwarf race that just barely fits the ticket
22 species on my list, and I am sure one could add a few more. Of course from this list there are hundreds of hybrids using these species, many will be amendable to growing as teacup Paphs.
I have been a student of bonsai for a long time, and it has taught me a few things that do cross over into orchids. In bonsai - the real effort is put into thoughtful presentation. The cross over into orchids is that you should groom your plants, and choose pots to show the plants better. It is possible to deliberately keep some of these Paphs healthy & blooming and force them to stay more compact. Growing a bit brighter will force tighter foliage. Don't overpot, take the time to wind overlong roots into the smaller pot. Remove more of the previously flowered, older growths. Caution on removing old growths, make sure front growths have developed roots, often the front growth or two don't have roots. Choose your pot size so that the roots system fills 50% or more of the volume. These are some tricks to keeping the Paphs tight and compact. Experiment !!! Remember - adjust watering schedule to the plant. Only a healthy plant will bloom, so be careful. Too extreme on this and the plant won't bloom, defeating the purpose of the excercize. Consider foremost that you are growing for an attractive presentation. In terms of hort skills, this is the next level up, once you have learned how to keep the same plant growing for 5 or more years, now it is time to really work on good presentation.
I have a 5 growth Paph armeniacum in a 4 inch tall, 3 inch diameter hand made ceramic pot. I deliberately wound the rhizomes around to make it fit, rather than simply potting up and letting it spread out. So far it has only bloomed one flower at a time, but when it does more, it will be quite a showpiece. Most of the above, with a little encouragement could make nice specimens in 3 inch or smaller pots. Give it a try.
