I think you need a reality check on what you are going to get from a couple of (relatively) tiny speakers compared to a pair of (decent) headphones.

In my humble opinion, you are simply not going to get anywhere close, especially without a sub.

So, how to get the ‘best’ out of them is an exercise in accepting there is no way it sounds anything like the headphone sound. After that, you are looking at trying to recognize when the onboard EQ or compression is starting to introduce distortion into the sound. Yes, you CAN boost the bass and cut mids and highs, and compress the bejeezus out of the signal, but truth is that if you get close to the headphone sound balance, it will distort at quite low volumes. Or the compressor will start to seriously squash the sound in an unnatural way.

Whether this matters is strictly your decision, if the audience is okay with the sound as is, you’re gold. There are some simple ways you can improve the sound without going to a full PA. A cheap TV sub (under $100) run from the main outs and blended in subtly can make a huge difference in fullness, help out the bass and drums. They are quite lightweight…

TBH, if seeking to get that headphone sound without breaking the bank and seriously upping how much gear you carry, a small TV sub is the way I’d go…