If it's anything like Portuguese, here we'd use the bottom 2 sentences more, and also "je sais français". In our context saying that you know french/how to speak it focuses more on the fact that you know the kanguage, whereas saying "I speak French" is more casual. I'm no native, though
in french when a verb directly follows another verb then the infinitive is used for the second verb
je dois commencer - I must start
Voulez-vous venir - Will you come
je voudrais parler aver vows - I would like to speak with you
À quelle heure vous allez être ici - At what time are you going to be here
Je vais préparer le dîner pour nous - I am going to prepare dinner for us
je vais être prêt bientôt - I am going to be ready soon
Vous devez attendre - You have to wait
Est-ce que je peux vous aider? - Can I help you?
It's in the infinitive whenever you use peux (can). So:
I can speak=je peux parler I can dance=je peux danser
Je parle is in the indicative only (I speak/I am speaking), nowhere else.
You also use the infinitive when you combine with je dois (I must), je veux (I want to), je voudrais (I'd like to), ...
(CMIIW about anything here) Firstly, "I can talk French," is improper grammar, because talk (in that sense) is intransitive, meaning it cannot have a direct object. Secondly, talk and speak are different verbs in French. "Dire" means to say and "parler" means to speak (talk has many definitions in english; in my opinion, try to avoid translating it). Even though they may seem interchangable in English, they are not always in French. E.g. "I will go" vs "I am going to go." Not interchangable in french, but interchangable in english.
"je peux parler français" means that you are up to do it, capable of doing it, ready to do it (if needed).
"je sais parler français" means that you have learned French, that you know how to speak French.
The difference is not huge, so it will be a matter of circumstances.