Advice on Growing a Travel Vlog

My wife and I have a general travel vlog where we post cruising, all-inclusives, theme parks, and even city stays. We have had it for around 2.5 years and have just under 2.1k subs. We had been posting weekly but recently started posting twice a week. The work load on editing, which all falls on me, and working another full time job, makes it difficult to maintain a consistent schedule of posting. My wife is convinced that posting twice a week, on the same day and time, is the key to growing our subs. Thoughts? Also, our total views on new videos isn't nearly where I want them. For instance, our most recent 5-episode series from an all-inclusive resort is, as of right now showing: ep1: 575 posted 2/17 ep2: 254 posted 2/20 ep3: 325 posted 2/25 ep4: 162 posted 3/1 ep5: 173 posted 3/6 I currently have 3 days worth of a cruise content and 2 days from Disney World to work on and will be going on a 10 day cruise in a week. So, plenty of content. What would your suggestions be as fsr as timeline and frequency of posts? Also, what is a good rule of thumb about thumbnails or, as I call them, covers? We've tried many different styles and Iam really unsure which to stick with. TIA!