What ever doubt means maybe it means less water twice is better than to much water once ?
The argyroderma is a heat loving sun pig and yes a fair amount of drinking is allowed for it this time of the year.

Yours is a tad thirsty I'd let water flush though on the edge of pot at night first. It'll be okay if it has to wait for more in the morning. Yours is inside it'll happily wait for more.. Argy is in it's growing season techincly you could drowned it if you wanted to as doubt can aslo mean better safe than sorry
Indoors ? For yours it might be better to use less water twice than more once Hmmm guessing you have it setting there for full sun outside transitioning

Lithops: You show the number one reason why each of them should be in there own pots as singles. How do you not water a lithops if you need to water a lithops ?

Thanks for your help! I will do as you suggested for watering my argy. Yeah I can only grow my plants indoor unfortunately, so I'll see how it goes, but good thing is they get good indirect sun throughout the day and if weather is nice 4 hours of direct sun, and I also have grow lights to help a bit. As for the lithops I know it's a tricky situation but I simply don't have more space on my window sill to put them in separate pots.. I will be very careful watering them and try to "accommodate" everyone's needs xD.

Might be worth it for you & maybe you could concider an indoor set up including lighting fans and such ?

After you add water your no lnger in charge of any lithops you intended to water or not water
Water has it's own rules it only has has to obey the laws of physics not yours