If I were to buy a nic that uses the Intel x540 chipset, which only supports 10GbE/1GbE/100Mb, with a sfp+ port, would the 2.5 gig ports run at full speed on my unmanaged 2.5 gig switch (https://www.amazon.com/gp/product/B0C861FKB1) that has a 10 gig sfp+ uplink port or would I be forced to get a nic that uses something like the Intel x550 chipset that supports 10/5/2.5/1GbE.

I currently have a Intel i225 ethernet controller in my main computer and would like to connect at greater than gigabit to my server/nas as the motherboard in that only has a gigabit port.

Examples:

I know that if I plugged my computer and another computer with a Intel x540 card together, they would auto negotiate to gigabit speeds as the Intel x540 does not support multi gig connections.

I also know that if I plugged the Intel x540 into the 2.5 gig switch over rj45, it would auto negotiate to only gigabit speeds as it does not support multi gig connections.

However, would connecting the Intel x540 to the spf+ port on the switch that supports 10 gig allow data transfer up to 2.5 gig to any computer that is connected to the 2.5 gig rj45 ports on the switch. Or, would any data transfer between the two computers over the switch be caped to only gigabit speed since the Intel x540 does not support multi gig.

I currently have multiple different computers connected to this switch that have motherboard ports that support 2.5 gig using controllers like the Intel i225-v and would like to upgrade my current server/nas to have a connection greater than gigabit. I know using the Intel x550 would work perfectly as it supports multi gig connections but I simply do not have the budget for it since it typically goes for $100 on Ebay. However, I would rather get a nicer nic than can allow my setup to expand to 10 gig in the future as I am otherwise forced to just get a pcie 2.5 gig nic using a controller like the realtek rtl8125b (I already tried a pcie card with the Intel i225-v and had issues).