Will I get benefits on Global SKU if I am using it as both FBM and FBA?

Yeah after converting the listing into FBA and if your SKU and ASIN are the same as the USA listing then your stock will automatically reflect in Canada.

If you have an ASIN enrolled in the Remote Fulfillment Program (RFP) in the USA and also have a Fulfilled by Merchant (FBM) listing for the same ASIN and SKU in Canada, converting the FBM listing to Fulfilled by Amazon (FBA) will automatically share your inventory in Canada.

when you’ll convert your listing then your stock will automatically reflect in canada.

As Mr. Kallis Roy, you have mentioned that the AISN and the same SKU is enrolled in the Remote fulfillment, if you converted the Canadian FBM listing to FBA then you don’t need to send the inventory saparetly to Canadian warehouse, if you get the orders from this marketplace then amazon will automatically fulfill them from this home marketplace.

Yes, your stock will automatically reflect in the Canadian market when you convert your FBM Canadian listing to FBA.