Church Latin likes the be easy and clear, that isn’t what happens with the jussive. Further, when the church wants to claim something that ought to be they just use the imp. not the subj. esp. when its not in the past.
For that, I will look elsewhere in the GIRM, to see if there is a clear distinction.
… and I’m not sure I’m finding it. Here’s a simple sampling, with subjunctive (jussive?) in
bold and permissive/preferential verbs underlined:
GIRM 117 (USCCB): The altar
is to be covered with at least one white cloth. In addition, on or next to the altar
are to be placed candlesticks with lighted candles: at least two in any celebration, or even four or six, especially for a Sunday Mass or a holy day of obligation. If the Diocesan Bishop celebrates, then seven candles should be used {the Latin does not have an additional verb here – japhy}. Also on or close to the altar,
there is to be a cross with a figure of Christ crucified. The candles and the cross adorned with a figure of Christ crucified may also be carried in the Entrance Procession. On the altar itself may be placed the Book of the Gospels, distinct from the book of other readings, unless it is carried in the Entrance Procession.
GIRM 117 (Latin):
Altare una saltem tobalea albi coloris cooperiatur. Super ipsum vero aut iuxta ipsum duo saltem in omni celebratione, vel etiam quattuor aut sex, praesertim si agitur de Missa dominicali vel festiva de praecepto, vel, si Episcopus diocesanus celebrat, septem candelabra cum cereis accensis ponantur. Item super altare vel circa ipsum habeatur crux, cum effigie Christi crucifixi. Candelabra autem et crux effigie Christi crucifixi ornata in processione ad introitum afferri possunt. Super ipsum altare poni potest, nisi in processione ad introitum deferatur, Evangeliarium a libro aliarum lectionum distinctum.
GIRM 301 (USCCB): In keeping with the Church’s traditional practice and the altar’s symbolism, the table of a fixed altar
is to be of stone and indeed of natural stone.
GIRM 301 (Latin):
Iuxta traditum Ecclesiae morem et significationem, mensa altaris fixi sit lapidea, et quidem ex lapide naturali.
GIRM 310 (USCCB): (Regarding the chair of the priest celebrant) Any appearance of a throne, however,
is to be avoided.
GIRM 310 (Latin):
Omnis autem species throni vitetur.
GIRM 333 (USCCB): For the blessing of sacred vessels, the rites prescribed in the liturgical books
are to be followed.
GIRM 333 (Latin):
Quoad vasorum sacrorum benedictionem, serventur ritus in libris liturgicis praescripti.
GIRM 334 (USCCB): The practice
is to be kept of building a sacrarium in the sacristy, into which
are poured the water from the purification of sacred vessels and linens.
GIRM 334 (Latin):
Mos servetur exstruendi in sacristia sacrarium, in quod aqua ablutionis sacrorum vasorum et linteaminum fundatur.
I do see the occasional usage of the future-passive-participle + est (the “passive periphrastic”) construct which means “should/ought/had to [VERB]”, such as here:
GIRM 297 (USCCB): The celebration of the Eucharist in a sacred place is to be carried out on an altar…
GIRM 297 (Latin):
Celebratio Eucharistiae, in loco sacro, peragenda est super altare…
I’ll compile more results.