Explanation of memento fiscal - Vos Obligations Fiscales and VAT with UK company

I have recently registered myself as a freelance auto-entrepreneur (entrepreneur individuel / micro-entreprise)  for business management consulting. I just work for myself and have no employees, and I do not sell any products.

ACTIVITE
Form juridique: Profession Libérale (1500)
Activité principale: conseil pour les affaires et management (code: 73202)

I received a letter in the mail with my SIRET number and other details.

However, I am confused by some of the acronyms under my ‘Obligations Fiscales’: BNC, TVA, and CFE.
I was hoping you might explain. The details read as follows:
TYPE D’IMPOT: Regime
BNC: SPECIAL - régime spécial des bénéfices non commerciaux - Numero (ROF): BNC1
TVA: RFB - Franchise en base - Numero (ROF): TVA1
CFE: VLF LIB - valeur locative fonciere des libéraux

A second (related) question is that I am unclear about the VAT in particular. I have just agreed to a 6-month contract for more than 34,400 euros with a UK company to provide management services - do I charge VAT from day 1 or wait until my income surpasses the threshold? Or do I charge VAT for consulting services at all with UK since Brexit?

Thanks so much in advance - I look forward to your reply.
Have a great day.
Dan