Will a 300 liter pr hours air pump whit 2 air stones be good for 19l oxypot DWC

It will be fine. More air isn't always better. It doesn't need to look like you're boiling the water. Too much dissolved oxygen can inhibit growth. Keep your temps 68-72F (20C). There is more dissolved oxygen available at lower temps, but under 65f (18.3C) you will start to see nutrient uptake problems (particularly Phosphorus). https://www.mdpi.com/2077-0472/11/11/1140/htm

Best aeration is when it looks like a bubbling cauldron. More the better. The silica air stones are usually the best, but need bigger air pumps.

maybe 2 small round ones.. they list recommended gph / Lph for the stones, usually.. or find similar sized and shape online and go from there. the small round ones are the 'easiest' to push... so lower gph / lower pressure needed for those compared to others. if your pump is going to work, it'll be with those. It really doesn't take much to oxygenate water. Gasses go into solution almost immediately then will oscillate around equilibrium of any moment (temp + pressure related). The bubbles also agitate, which make microbial growth more difficult. Small bubbles for oxygenation, large bubbles to agitate (stagnant water is bad)... imho, you could just coil a 1/4" tube weighted at bottom and poke some holes in it... trial and error with pump how many you can poke. But, this would be easy to well-distribute bubbles and won't clog up. O2 is less of a concern given dynamics of how easily gases go into solution.