Can 4 Joy cons connect to the same Switch?

When connecting controllers to the switch, it shows 4 slots for controllers. Is it possible for:

• All of them to be a sideways joy cons
• One of them to be a joy con pair and two of them to be sideways joy cons
• Two players to play using two joy con pairs

Without using multiple switch systems?

I’m aware that you can connect pro-controllers to the switch to allow for 3 or more players, but is this possible with a second pair of joy cons?

You can use up to 8

I have tried this recently. You can use these joycons in any orientation you want. Such as use 3 pairs of joycons (6 total) and 2 side ways ones. You can't have 8 pairs since that is over the 8 total limit. But you can certainly do 4 pairs like you asked about.

The limit is more about the number of players, as most games only allow 4 players at a time per Switch system, but those 4 players can have either 1 or 2 joycons as their controller inputs, meaning the switch will accept up to 8 joycons paired with it.

Up to eight wireless controllers can be paired to the Nintendo Switch console at a time. However, the maximum number of controllers that can be connected will vary depending on the type of controllers and features that are used.

Source: Nintendo