I'm not an expert of any sort, but let me try to answer according to what I have experienced so far.
1) Is there action during all day?
: For warzones, pretty much. For solo arenas, 5pm~2am on weekdays, 12pm~2am on weekends.
2) Doest the SoloQ Pops quick?
: It would depend a lot on your ELO, but in general, during the time interval I have mentioned in (1), yes. There is always at least one or two arena matches going on.
3) Is the pvp balanced? Republic and Imperial in almost same level or is it unbalenced like pot5?
: Imperial side seems to have more pvpers overall (Mainly due to 2 reasons : (a) number of talented pvpers on the republic either quit playing or moved to the imp side post 2.0, (b) the imp side have a larger population in general). The ratio between good:average:bad pvpers on both sides is similar. Since the population is very small, it all depends on whether some group of skilled people are Q-ing on one side or not.
4) Is Jung-Ma more populate then Pot5?
: I haven't been to Pot5, but no. Probably lot less polulated than Pot5, which is considered as one of the major servers. There are some websites that provide precise statistics, so might be a good idea to visit them.
Summary:
If you want to enjoy arenas just for fun, I would advise against moving here since the frequency of the pops and the variety of people you would see in them would be lot less than Pot5. But I guess you could get lot of rating easier in this server just by checking who are currently being Q-ed for arenas. ( As a pub, for pub vs imp games, it is usually an easy win if certain players on the imp-side are not Q-ing.)