I have L2 switches which will be daisy chained together (yes I know,
daisy chaining isn't great, but anyway..) The L2 switches will then
link to a L3 switch.
Both the L2 and L3 switches have x4 10GbE SFP+ ports.
Something like this?
+------+ +------+ +------+
| L2 |SFP+----SFP+| L2 |SFP+----SFP+| L3 |SFP+-----Server with SFP+
+------+ +------+ | |SFP+-----Server with SFP+
Would I be able to daisy chain the L2 switches together using the SFP+
port with an Ethernet cable?
If the switches are ethernet switches, then the only cables you can use are ethernet cables. Remember that ethernet runs on a variety of media, including UTP and fiber optic cable, so any cable used for ethernet is an ethernet cable.
Also I was going to link the L2 switches to the L3 switches via Fiber
using the SFP+ ports. However in some cases, that maxes out the L3
switch, and I need at least 8 SFP+ on the L3 switch, so is this just a
case of adding extra SFP+ modules to the L3 switch?
Based on your description, I do not see the need for eight SFP+ interfaces in the layer-3 switch. Whether or not you can add SFP+ interfaces to the switch depends on the switch model and if it has slots for more SFP+ interfaces.
Layer-3 switches are first layer-2 switches, but also have an internal routing module. Other than that, the switches are switches, and you can use the SFP+ as switch interfaces in either type.
I also have two different servers, one which have 10Gbe port and one
with 10Gb port, would I be able to connect these to the L3 SFP+ via
That depends on the server hardware, which is off-topic here, but if the server NICs have slots for SFP+ interfaces, then there should be no problem.