Right, an FLGS is going to run an escalation league & the first round is 20 Power Level & must be a valid battle-forged detachment from the BRB, with the next rounds increasing by 10 PL up to 60 PL. My initial thought was run 2 Sisters of Silence squads, but as they've no HQ, no battle-forged for them.

So, my options are; Sisters of Battle (yes, I have some) or some variation of Space Marines. If I went Marines I was contemplating using Primaris, as they're new to me. Though I doubt the effectiveness of a Primaris Leftenant & 2 Intercessors squads, which were my thoughts went to first.
Yet, a Primaris Leftenant & Intercessors squad might be a better second detachment, which is allowed at 50 PL points.

Argh, list building, just one of the things that stop me from playing.

Edit: Currently, I'm fixating on the following army format HQ+Troop+Heavy. Which with Sisters means, Cannoness, a 10-unit or 2 5-unit BSS & the Pipe Organ of Doom(Exorcist), SM: a Captain, a 10-unit or 2 5-unit Tactical Squad & a Whirlwind, Primaris: Primaris Leftenant, an Intercessor squad & a squad of Hellblasters.
Yeah, I'm thinking the list with a tank, is probably the better one at 20 PL.