(Or if you can afford it, just get a better physical keyboard layout, and worry about the logical layout only after you have a physical layout that you like.)
^^ This.. I see people putting quite a lot of effort into making the standard layout better in increments, with limited results and very little real world benefits. Putting the same effort into deciding which of the properly ergonomic designs out there suits you most is more beneficial, although I admit there aren't many good examples commercially available.
This thread may help you decide which factors are important to you: https://geekhack.org/index.php?topic=73447.0
1. The ErgoDox is decent, but suffers from a poorly designed thumb cluster (hard to reach far keys, closest are the only comfortable ones) and not enough stagger on the pinkie columns, among other things.
2. The Axios is not available yet. Seems to be trying to accommodate too many different people's wishes, so may be a bit too "generic" or having too many features when released, with some of the same issues as the ErgoDox, despite being modular, but better in terms of thumb cluster being both modular and movable. Good overall design by an active GH member.
3. My own design will eventually become a product, but I can't make any promises as to the timing yet, so it's probably best not to consider it being available for at least 6 months.
4. Kinesis Contour / Advantage. Rubber dome F-keys, curves not quite tight enough, thumb cluster angle not optimal. Fixed splay and tent angles, relatively large.
5. Maltron. Expensive. Also fixed splay and tent angles, but they're chosen well and in all regards besides price it's better than the Kinesis.
6. Truly Ergonomic. Not truly ergonomic. Small and fixed splay and tent angles, not optimal by any means. Lack of keycap replacement options. Some people have had issues with the newer versions, AFAIK they're using clone switches now, too. Not enough stagger on pinkie columns. One nice thing is the placement of arrow and edit clusters.
7. Keyboardio. Matias switches, custom keycaps and very few replacement options, but it's a nice design. Flat thumb clusters, relatively expensive, semi-fixed splay angle and limited default tent options, but you can make your own supports, so it's a lot better than the Truly Ergonomic in this regard. More accessible thumb keys than ErgoDox.
8. King's Assembly. NOT ergonomic, so it shouldn't even be on this list, but I thought I should mention it so you know about it, since it claims to be an ergonomic design.
9. Katy (K80CS). Very nice design, but not commercialised yet.
10. Atreus. Great little 40%-ish ergonomic design for a good price and some of the proceeds go to a good cause. Some may find the number of keys limiting. Fixed splay angle and not tentable, but very compact.
11. Various other "in the pipeline" or extinct designs. Not available, but useful for seeing boards based on different ergonomic or supposedly ergonomic factors: https://geekhack.org/index.php?topic=55099.0
So, IMHO, the best options currently are the Atreus for a portable, Maltron if you can afford it, and probably the Keyboardio or Axios when it finally gets released, but it all depends on your own personal requirements for a board. I'd promote my own design, but as I say, it's not quite ready for productisation. If you're up to DIY, I highly recommend it, though
Then we get to character layouts... that's a whole other kettle of fish, but not as important as the physical layout. Best discussed once a physical layout is chosen, since the optimisation is very dependent on the placement of physical keys.