The non offset are for standard Z4's, the offset lollipops are for the Z4M, however the offset bushing can also be used on standard Z4 as well.
BMW had Meyle or Lemfoerder as OEM suppliers.
You can purchase the offset rubber bush insets separately fron bmw, £55 last time I checked. Getting them pressed in isn't too much effort unlike the E46 bushes that are fliud filled.
I ues Powerflex, easy to fit and they drive well. They are rrp £150 ish but there are deals to be had, mine were less than half of that and there is a lifetime warranty.
I am unable to find powerflex for our cars. Only for non M z4. Non m are not offset which changes the geometry. Do you perhaps have a link? Actually powerflex told me tonight they do not make bushes for M cars only non M
Those are the ones you want though I’d go on eBay and you’ll likely get them cheaper, especially if you wait for discount codes which come up quite often.
I’ve had them on for a few years and been fine for road and occasional track usage. Go for it, plus as said lifetime warranty.