301 redirect vs PBN backlink

I have many sites... but the 3 here I have

1. Established site no1 - needs more good backlinks ( original idea was to link from the aged and niche relevant domain to this )
2. Aged domain - Just registered strong backlink profile ( TF30, DA25 and kind of niche relevant to site No1 )
3. Brand new site - Not even live yet but it will be good and I really want to be able to compete in the rankings ASAP.

What do you think is the best option? use aged domain as 301 redirect from 2 to 3 or use it as part of a pbn to link to no 1?

My idea of doing the 301 would hopefully allow me to start link building sooner with site no3
But I have a feeling that 301 will be a complete waste is site number 3 does not work out for any reason

Question is not clear.
What do you want to achieve ?

If you want to start a new website, I would go with option 2 only , reducing the risk of any 301 automated google penalty.