I am partially answering my own question, and will update w/ more info as I discover it.

We predominantly work with Japanese character sets and the existing font-family used in the pos.css file (e.g. 'Inconsolata') did not render good results. I found this stackoverflow article (stackoverflow.com/questions/14563064/japanese-standard-web-fonts) which indicated a best practice was to use:

font-family:"ヒラギノ角ゴ Pro W3", "Hiragino Kaku Gothic Pro",Osaka, "メイリオ", Meiryo, "ＭＳ Ｐゴシック", "MS PGothic", sans-serif;

So far the results in the UI are better but more testing is need on the printers.

Try enabling the print using proxy on PoS terminal and using this app for communicate directly with hardware: https://github.com/Fedrojesa/ProxyPoS

Very high quality as you are using the build in printer features.