The preamble states:
The seasonal theme words, A and B, each have three sets of unclued variations, derived in a consistent way, indicated by 1, 2 and 3. One of the ‘3’ variations has two otherwise valid alternatives. The puzzle title provides the total for the first three characters in the same format to confirm the alternative that solvers must use.
Solution grid and notes
The theme is the popular Christmas carol, The Holly (A) and the Ivy (B).
Variation one are words which can be added:
(A) HOLLYWOOD and HOLLYHOCK; (B) IVY LEAGUE and IVY-MANTLED
Variation two are familial plant names:
(A) ILEX, MATE and YAUPON ; (B) ARALIA, PANAX and HEDERA
Variation three replaces the roman numeral components of HO(LL)Y and (IV)Y to form new words.
(A) HOMILY and HOLILY ; (B) VIVIDLY and CIVILLY
V+I+V = 11 (or XI) to eliminate the possibility of LIVIDLY