Can the two SFP ports on this switch be used together for higher uplink speed?

Yes. The two 1-Gigabit SFP ports can be aggregated together for a connection speed of up to 2 Gbps.

How many PoE+ ports does this Luxul switch have, and what is the maximum power per port?

It has 16 Gigabit PoE+ ports, and each port can deliver up to 30W of power.

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Luxul 1Gb L2/L3 Managed Switch - 16 PoE+, 2 Combo RJ45/SFP Rear-Facing Ports - TAA Compliant SW-505-16P-R

16 Ports - Manageable - Gigabit Ethernet - 1000Base-T, 1000Base-X - 3 Layer Supported - Modular - 2 SFP Slots - Twisted Pair, Optical Fiber - PoE Ports
Luxul 1Gb L2/L3 Managed Switch - 16 PoE+, 2 Combo RJ45/SFP Rear-Facing Ports - TAA Compliant
The SW-505-16P-R is a 16 port PoE+ rear-facing single-space rackmount 1Gb switch with 2RJ45/SFP 1Gb ports (aggregable up to 2Gbps) with a total PoE power budget of 185W. Each of the SFP ports can be used alone or aggregated together up to 2Gbps. This L2/L3 switch with 36Gbps switching capacity provides VLAN, QoS and other powerful management features. Up to 16 switches can be grouped in a single pane user-interface allowing easy and comprehensive administration. Variable speed fans for quiet operation. ACL ingress filtering.
Designed to support AV-over-IP (AVoIP) applications, the SW-505-16P-R includes 16
1-Gigabit PoE+ Ethernet ports, two non-powered Ethernet ports, and two 1-Gigabit SFP
expansion ports (SFP and non-powered ethernet ports cannot be used at the same
time). Both 1 Gb SFP ports can be aggregated for a connection speed of up to 2 Gb.
The 16 PoE+ ports deliver both gigabit data and power over a single cable to 802.11af/
at-compliant devices, with a maximum of 30W per port. For separately powered devices,
these ports deliver network connectivity only. The total power budget is 185W for all
PoE+ ports combined.