Which pillar: 2nd or 3rd have higher yearly yield on average? I guess it depends on the pension fund/bank that you put your money in, but are there significant differences?
From tax deduction perspective, I suppose, both pillars give the same benefits?
I guess the same applies to transferring funds to buy property, founding own company or withdrawing money when leaving the country, correct?

Both ain't got no yield no more, yields were long killed by central banks. 0.2-0.5% so called yield is a spit in your face. Let's be frank, a one time tax saving is the only thing you're getting out of it. And even that is not certain - what if your new country after emigration just taxes away your whole payout? It can happen.

Out of the two, pillar 3a is better, fill it first if you must - less strings attached and many banks allow you to freely buy/sell their stock funds with it. Pretty expensive funds, as you might guess, there's little competition and strong bank lobby