I understand now.
The important decision is how many pairs would you like to have open at the same time. I would recommend to have 10 pairs open at the same time. This is _not_ implicitly related to how many pairs you have in total in your portfolio.
This means, you set max slots to 10. It will allocate 1/10 of the account to each pair opened (so 10k per pair, 5k per leg). Because you have Reg-T margin, you only need 50% of the position in margin (you effectively "control " 200k of capital). So if you keep your margin at 50, it will actually open positions twice as big = 20k per pair (10k per leg) - because of the trading on margin.
I would set your strategies just to use one single slot. If you have pairs you trust more than others, boost it to higher value (1.5 or 2) for them.
PTL Trader will now trade 50 pairs, but at one single time you can be only in position in 10 of them. Which is OK (we can call it "overbooking", because you are not always in position for all pairs). This way you can get the most from your capital. When your account is fully saturated (10 slots used), it will ignore entry signals until some slots are free again.
I would not trade less than 10 pairs at the same time, because of the risk/diversification. In this setup, if one pair suffers a big loss, it won't affect your whole portfolio too much.
About this:
I have 4 :1 reg T margin.
Beware - Reg-T margin has 25% margin requirement for intraday trading only. For overnight positions, it increases to 50%. So you have to set the margin to 50 anyway.