This is not really WaveLab related but I always deliver EP and album masters for approval in two formats.
DDP w/HOFA DDP Player. It’s not an “online” method but I simply make the DDP in WaveLab and then embed a HOFA DDP Player that allows them to download and listen to it, and/or burn a CD. Steinberg offers a free DDP Player too but it strangely does not burn CDs. I deliver a DDP even if they are not making CDs because a DDP in a DDP Player is a great way to approval all aspects of the digital master.
Or the more modern approach is this:
I and other mastering engineers have been working closely with Samply to help fine tune a mastering focused player. After you render a WAV file of each EP/album track, you can upload to Samply and it streams the audio in full resolution and doesn’t add ANY space between the songs, so it’s perfectly gapless. You can upload an EP or album of WAV files and they’ll play back seamlessly in any web browser on a computer or phone. Even songs that crossfade play back without a tick or pop, let alone a large gap due to buffering etc.
It’s been a tremendous help for the last year or so getting mastering approvals as so many clients just want to do everything on their phone or iPad and can’t handle doing something that involves more than one click or reading instructions (DDP Player).