I’ve used a fair bit of glasses and I think the answer to your question, only you will know your the answer.
I’ve never been comfortable with 35mm because I feel it’s still alittle too tight. The 24GM is to me, my go to lens during my travels as well as events because its just the framing I want. So it depends on your self.
Physically, the lens is a joy to have. It’s light weight, allows me to shoot in poor lighting, and one of the cheaper prime f1.4 Sony GM /Zeiss lenses. There’s no other lens (to me) that can offer me any other alternative. That’s one I bought it on the day it was launched.
Whether to sell / keep the 24-105 really depends whether you can live with the advantage of an additional stop if you get the Tammy but lose out on the 105 reach. It’s best if you review your shots, and check what’s the length you normally shoot. If a majority of your shots are at 105, then perhaps you’d miss the reach of the 24-105 if you sell it.
If it’s my choice, I’d sell the Samyang in a heartbeat, get the 24GM. I’ll probably keep the 24-105 because of it’s reach, and up my ISO if I’ve no choice. If the exposure is still under, I’ll tweak it at post production.