Will "spamming" in multiple chats will get my bot account banned?

[sundheden]

Refering to this for joins:

The final answer on JOIN limits

Yes, that is still the case. Per IP, I believe 15 second buckets. JOIN and PASS are counted IIRC 40 JOINs sent in one command would be counted as 40 individual joins as far as the rate limit is concerned.

And this for per connection limits:

• If you send more than 20 commands or messages to the server within a 30 second period, you will get locked out for 8 hours automatically. These are not lifted so please be careful when working with IRC!
• Mods can type 100 messages in a channel before hitting this rate limit. If a message is sent to a room in which your global message count is already too high, you will be disconnected.

https://help.twitch.tv/customer/portal/articles/1302780-twitch-irc

You can create multiple instances (run the bot twice as you say) and get the message limit per connection/instance. However, the JOIN limit will be limited per IP, hence “both instances” together.