I’d be interested to see your PHP Configuration readout. You can get this by creating a file in your Magento Root Directory, which will give you a readout. Check this post for instructions on how to do this (PHP Troubleshooting (How to find important information)). The results may highlight something useful.
It’s also worth creating a support ticket to Cloudways and ask if they will setup a 512MB or 1024MB swap file for you. This “buffer” can often assist in low PHP environments by sacrificing some disk space to act as additional memory. It’s a 2 minute job that might save you the upgrade costs.
What I can’t wrap my head around though, is that all of my Dev Servers (and the Sandbox server I use for creating videos) are all running on 2GB RAM - So, you shouldn’t have any issues there. Having said that, I just remembered that Cloudways servers also might be running Varnish, ElasticSearch and other services that’s eating into your 4GB.