First of all, congratulations on becoming a soldier! As for the Beijing Political Headquarters you mentioned, it may refer to the Political Work Department of the Central Military Commission (CMC) in China, which is the political work organ of the China People's Liberation Army and is responsible for the political, propaganda, organization, mass and security work of the army.

As for the arms you will join, I can't give a definite answer because you didn't provide more information. But generally speaking, the arms of the political work department mainly include political cadres, propaganda cadres, organizational cadres, cultural cadres and security cadres.

As for whether this unit is good or not, this is a very subjective question. If you are interested in political work and willing to develop in this field, then this unit is very suitable for you. If you are more interested in other military aspects, then this unit may not be suitable for you.

Finally, about the way out, it depends on your personal ability and career planning. Soldiers of the political work department can hold various positions in the army, including political instructors, propaganda officers, organization officers, cultural officers, security officers and so on. You can also choose to leave the army and go to work in related fields. In any case, the way out is broad, and the key lies in your efforts and ability.