when i was testing this was using my friar as basis
which has 48 ench and rr3 with +2 bonus with aug dex 1
for base dex buf it has max bonus of 62
and for spec dex buf it has max value of 93
yet when i cast them without any ench bonus i am geting 150 dex
which is 4 fom aug dex 1 58 fom base dex buf and 84 fom spec buf
so with this info also chked spec dex value on sple lst as 69 value
and when divided its vaue to its base spec points(69/45) i get 1.53 roundded down value which actualy fitng on level based progresion of spec buf value

so if i get 61 ench in total i will be caping spec buff value as 93 dex and qui
and also at 60 ench base bufs cap as well so actualy + ench seems working at a degree

Selfbuffs should be strict min(delve*1,25 , specbuffcap).

+ench should only affect basebuffs of the friar.

yep it suposed to be what you said yet it si incresing via +ench and also dont forget slef buffs not givng cap buffs even you had 50 ench +20 on a seting with out buf bonus fom old ras or toa buf bonus they suposed to cap around 153(2 points always mising whihc was alwys i hated on old frontier with my friar even after rr5 that was stil 153) that problem occurs duo to lver value on selfbufs then castable ones
selfs has 69 value on their last counter part(red one) but castable one has 75 value which makes selfs wont cap with high ench.
also even if yuo make your ench 50 on term of item and skil it only caps base buf after 50 it is effectin in increment of selfs i was used to test it on live with a robe i found at sid which was givng +6 ench bonus and when i swith it it was incrisng self about 2 points also here i tested it with my 48 ench +2 fom rr bonus +2 fom an ench givng staf its value incrsed 82(with out staf) 84 with staf