Here's the difference:

Spirit Animals are there most of the time and talk you through things they are sometimes like inner thoughts. They can calm or anger, weaken or strengthen.

Weak usually goes with calm. And anger usually goes with strong.
If you know the past of your spirit animal without asking them first they are most likely your past life. Its close to impossible.

Spirit Guides usually don't give their name. They either give advice in code or extremely straight forward. And protect you in the spirit world which is kinda like dreams but not. Depending on the level of guide they are usually prideful ( mostly only high level guides).

They can be regular animals or creatures of a spiritual plane.