Two 52 port gigabit Netgear GS752TS stacking switches, design options for two gigabit uplinks?

I would like to ask some experts for opinions about how to improve this network setup, I am looking after a smaller project within a larger company with limited communication between ourselves and the central team, I have decent sysadmin knowledge but am not a networking expert.

The main business premises is running from a large Cisco network switch with 9 x 48 port gigabit cards managed by central team. Our team is running a smaller specialized cluster of approximately 70 machines across two Netgear GS752TS stacking switches, unfortunately it is not an option to move these machines to the main Cisco switch which is already nearly fully utilized. Our smaller network, say we call it network B is all on a single subnet and VLAN, our Netgear switches are simply acting as dumb layer 2 switches.

Our Netgear switches have 52 gigabit ports however ports 51 and 52 can also be used as 2.5 gigabit stacking ports for a combined 'stacking' bandwidth of 5 gbps between switches. At the moment we are operating in this way with a single gigabit uplink back to the Cisco switch. We monitor usage and the 5 gbps stacking bandwidth between switches is sufficient however the issue is that the 1gbps uplink easily becomes saturated.

I would like to introduce a second uplink to the main Cisco switch, preferably there should be one uplink per switch so that the stacking bandwidth is not used for external connections, in other words, we would like to allow the following scenario. Somebody on the main network is downloading from a host on Netgear switch 1 at 1 gbps, somebody else on the main network is downloading from a host on Netgear switch 2 at 1 gbps, meanwhile various machines on switch 1 and switch 2 are communicating amongst themselves using 5 gbps burst bandwidth as part of cluster operation.

It seems the easiest option, say Option 1, would be to create a link aggregation group (LAG) with one link going to each Netgear switch. We can easily configure the LAG as static or LACP from our side, ie. the Netgear switches. Unfortunately it seems that this option would also require matching configuration on the Cisco side which the Central team will not allow, this seems to rule out the LAG option, can somebody confirm that setting up a LAG will require configuration on both sides of the link?

Option 2 would be to logically split the network so that so that hosts on switch 1 use the uplink from switch 1 and hosts from switch 2 use the uplink from switch 2, I think this could be achieved by setting up two VLANs, one on each switch. How would I make sure the 5 gbps stacking link is used for communications between switch 1 and switch 2 if they are on separate VLANs? Also, can I setup two VLANS to use the same subnet? In this scenario, the VLANS would only be used as a workaround to allow two uplinks using the MST protocol which I hope I am understanding correctly.

I hope this question is appropriate for this sub, I have read the sidebar and I think it is OK.