Look on youtube theres absolutely loads of videos on this at the moment. Plenty show what they use. Total boat seems popular but any marine epoxy should do the trick. The black dyes look quite cool as pure filling epoxy. I wouldn’t go clear cos you’ll see all the bad bits, whereas black then sand the whole top should look great.
As above, you need to tape the base and you will need lots more than you think. If you want to do a quick job in situ on really small cracks id use something like devcon 5 minute, mix it and allow it to harden for a couple of minutes then apply it in a couple of layers, it wont look as good but it shouldn’t run through the wood so much.
Ive used the colour matched wood filler before and its probably better for small gaps, i’ve also used the oak flooring sealant from screwfix which works and looks surprisingly good but cant see it holding up to kitchen table abuse.