No matter what strat you play ideal BPT is determined by acreage.
Your finishing acreage should be estimated at the beginning of the set. Estimates vary depending on what server you're playing and whether you plan on going all-x or doing x # of grabs per day or 1 PS per day or a couple of grabs & a PS. Once you've set a land goal you decide how many cs you need to build (as quickly as possible while still getting your economy going).

The formula is: Ideal BPT =sqrt(AcresToBuildOtherThanCS*GvtCS/4)
GvtCS
Normal 1
Theo 1.4
Dict 0.7

This chart works well for all Gvt except Theo & Dict

acres ---------------CS
0 -- 400 ------------ 20
401 -- 900 --------- 40
901 -- 1600 -------- 60
1601 -- 2600 ------ 80
2601 -- 3600 ------ 100
3601 -- 5000 ------ 120
5000 -- 6400 ------ 140
6400 -- 8200 ------ 160
8201 -- 10000 ---- 180
10000 -- 12400 --- 200
12401 -- 14600 --- 220
14601 -- 17000 --- 240
17001 -- 20001 --- 260
20002 -- 23001 --- 280

While I'd love to take credit for the formula & the chart The formula came from a spreadsheet I got from slag back at 2025 & the chart came from a post by patience also back at 2025, both around '07 or so. Although changes have been made here at EE I still feel this info is fairly accurate.