You may need the signal repeater - pair it with ST and it should be used by the Mesh and improve the signal strength for all your Zigbee devices.
You can pair the Ikea remotes with ST, and use them to control the blinds - there’s a community ST app for the Ikea remotes - search this forum - and Smartthings also support it now officially as well (open/close remote)
Think of it like a valve for light - 100% means all the light is coming through and blinds are up, 0% means no light and blinds are all the way down. This is common practise amongst all suppliers of this type of device.