Do y'all think this will be better to watch than the og or is the og still worth to watch? And was the og adaptation of Urusei Yatsura a complete one or will this be the complete adaptation of the manga?
No, you don't have to watch the old one to enjoy the 2022 version. The 2022 version is supposed to be full reboot/remake and as such one can expect it to be pretty self contained.
The series is also more of a episodic rom/com than anything and consists of many standalone stories that can be simply cut out without losing to much, as such I also wouldn't be too worried about the smaller episode count. If anything it might do for a better more concise experience, rather than a dragged out one.