Quitting Mirtazapine and starting a new antidepressant

So I’ve been on 30mg of mirtazapine for almost a year bc of depression, insomnia and anxiety and it changed my life. But recently the side effects bothers me a lot (especially the weight gain). Talked to my doctor today and he said I can start to taper off today and in 3 weeks I will be off them. He said I can try another antidepressant instead. I have a lot of questions. So my questions is:

1) How does it effect you mood when quitting antidepressants? 2) Which antidepressant is the best if you don’t want to gain weight? 3) Which antidepressant is the best for anxiety? 4) If you have quit mirtazapine and started with another antidepressant can you tell me how it felt and what you started?

Thanks a lot:)