Hello, i'm planning to buy the case SilentiumPC Signum SG1 TG. it has two fans already installed but I don't know if it will be possible to connect them to my motherboard, MSI B450 Gaming Plus Max. The fans in this case are SilentiumPC Sigma HP 120mm i think. Apart from that I'm thinking about buying two more of these but I don't know how many I can connect if I can at all. It would be nice if someone could help me as I can't find any info on that and I am just a novice.
Since your board has 4, 4 pin fan headers they can support PWM fans but you can also use them with DC control so if you only have 3 pin fans they will work too. The only thing is fans don't always start with low DC voltages so it may limit how slow you can set some fan speed.
Another thing is you can attach more than one fan to a header with a splitter. You can usually attach up to 4 fans to a header if they're low wattage/current draw (like .250A or less) so make sure you check fan current draw first. If you have no idea what you're doing just limit yourself to 2 fans per header to be safe.
One of the fan headers may be intended for a CPU fan/pump. It would be special as it may be monitored by BIOS and if no fan (RPM) is detected at POST it won't start the computer. It might also have an alarm associated with it so if RPM falls below a preset (usually something like 200RPM) it will alarm. As you can tell, it's usually best to reserve it for CPU cooler fans and/or pump and nothing else.