1) You can choose fixed capital, or other capital allocation methods
2) 4 x the cumulative max drawdown on each system is a good rule of thumb for equity allocation.
After trading full time for 17 years, my observation is traders who over leverage do not survive. Remember also that out of sample performance tends to be worse than in-sample performance. Especially when you are new to trading and are not aware of why systems can go so badly out of sample. (My recommendation is don't trade until you have walk forward a system and stress test the system on other time frames or markets.
This you tube video shows how to improve out of sample performance. Much of the video relates to GSB (Genetic system builder), but the principles can be applied out side of GSB. see https://www.youtube.com/watch?v=HDeJpONE090
Some systems have very high open trade draw-down, so its best to use open trade draw down for overnight systems.
3) As you can’t trade more than what margin your broker gives you, we the portfolio will not exceed margin requirements, and draw down * 4. If you don't want to use draw down for capital allocation set it to 1.
4) Static margin assumes you will have margin should every system trade at the same time.
Dynamic margin assumes that not all systems trade at the same time, so we can find the max margin figure that was used in past performance. Note one of the many dangers in exceed this is that on big moves, many systems trade & you get high chance of winning trades. On small moves the chance of loosing is much higher and few systems trade. This means trading > margin leads you getting all loosing trades and missing out on some big winning trades.