[digiKam-users] preferred format iOS pictures heic or png

[LCK AankopenEnRegistraties]

Hi, a newbie here so sorry for any lack of understanding about typical digiKam-users habits.

I want to extract/export all pictures (10.000 in original formats mostly NEF, the others JPEG, HEIC) held in MacOS Photos, using EXIF (so no sidecars holding XMPs) as result. And then import those in digiKam.

The digiKam manual (2017 version) tells me the best format to manage pictures is PNG.

In MacOS Photo’s export facilities there are two options:
1. "Export the original picture" (generally advised; the result in my case are the NEF, JPEG and HEIC formats). A specific (iPhone HEIC-formatted) picture I selected has a size of 2,4MB.
2. "Export the picture" (if modified the modified one), where the format PNG can be selected from the listed JPEG, TIFF and PNG. The same HEIC-picture as above saved in PNG format has a resulting size of 14,7MB.

The HEIC-format has ‘better’ compression characteristics than previous issued formats, including PNG, I understand. I have read (digiKam website) that digiKam can handle Apple’s HEIC-format. But the difference with the PNG in size is staggering (to me). Will I loose anything if I choose HEIC?

Questions: 
A) concerning all the NEF-formatted pictures I have, should I use NEF(RAW), HEIC or PNG as targeted format (in digiKam)? Or should I leave the format as it originally was and leave it to digiKam to manage these different formats every time I open a picture?
B) if I take pictures with an iPhone, what should I do in terms of required format in digiKam? Change to PNG or leave it as it was, meaning the HEIC format?

TIA

cortjan

[MacBookPro 16’' (2020) running Big Sur; Photos v6.0; iPhone 11 Pro Max. Waiting for digiKam 7.3.0 for first-time use]