San Miguel de Allende end of months

We (retired couple) are traveling to CDMX for two days and SMA at end of month. Questions .

1). Will take bus to SMA - is it advisable to buy bus tickets in advance or should we just show up at station (Central de Autobuses del Norte)

2. Staying at Airbnb for one week? Any recommendations for must sees? We plan to go to Guanajuato.

3. Finally is vibe in SMA similar to Ajijic, Jalisco. we visited there last year.

Gracias por su aura