Not sure what you mean by using silicone for strain-relief and protection? Are you blobbing it onto a connector or something? If you’re trying to keep a connector mated, I’d normally either swap to a connector with positive retention clips or I’d just keep the cable strain relieved near the connector with cable ties.
At work we use heat-shrink for bulk insulation. If you need water tightness or strength in tension then glue-filled heat-shrink works well. Heat-shrink also provides decent mechanical protection, although normally that’d be combined with careful cable routing and clips/cable ties to retain it in place, as well as things like rubber or plastic grommets or cable-glands for going through holes in sheet metal etc. Short lengths of flexible conduit for larger cables, often in orange for HV stuff etc. Fibreglass braided tube can also help provide mechanical protection/insulation where high temperatures occur, but it’s a bit of an annoyance to work with.