How to increase yield?

Compared to 2L pots, probably, all other factors the same. Go for 11-12 liters, whatever the standard size is in metric. That's plenty pot for an autoflower. Some autos are just small plants, and if you don't have some competency keeping plants healthy, autoflowers aren't the best option if yield is important. Since they flower on their own will, there's less room for error. Autos are better for growing out of season outdoors. if you have all killer plants, you can control things that result in 50-70g/sq ft. Random from-seed plants may not reach those levels due to genetic diversity. The only consistent way to hit the high marks is to grow known clowns with heavy yields. If you pull ~200g from a 2x2, you know you are doing what you can to maximize yield. If one plantn doesn't fill their area of responsibility well, you'll fall short. Try to be honest about the assessment and you won't beat yourself up about it too much.