To better load images up to a new web site I am told they have to be 72dpi
Ppi (dpi) is metadata used when printing to calculate print dimensions. For screen viewing, ppi is meaningless, only pixel dimensions matter.
So you can set the ppi to 72 - or any other number.
and not more than about 150kb in size else people wait too long for images to load.
With today's internet speeds, 150 kb isn't very big. But keep your files as small as possible, without sacrificing too much quality.
Personally, I'd go for a higher quality setting than 50, try 60 or 70. It also depends on subject matter - flat areas like a clear blue sky will compress really well, but may require a high quality setting to avoid artifacts/blockiness.
So, is there a "better" way to do this from within LR CC?
Yes, use Export. You can create presets for different sizes, quality settings, etc.
LR's output sharpening for screen is excellent. When capture sharpening is done properly in Develop, images should look good with standard output sharpening. If you're not pleased with an exported file, change the settings and export it again.
You could also LR's web galleries (with which I have no experience), but I get the impression that you want to upload the images to pre-built galleries, then Export is the way to go.
I am keen to learn more about this Web Gallies as having run one WGallery out I did not really understand it!
But as you say, these maybe for formatted (?) web sites with web galleries (?).
Interested that you use Export from within Lr with some presents.
Am I correct in saying these Presets have to be built / established within Lr or can they be imported for elsewhere?
Thanks - I'm off for a wander in the hills for a while if I don't get back to you today - plus it's St Patrick's Day so there's a Guinness (or two) to be had on my return!
I took a quick look at the LR web galleries, and they are made with thumbnails, big images, design, etc, and you can upload them complete to your website.
If you use export, you have to export thumbnails and large images separately, to folders on your harddrive.
Then you'd have to upload the images to your website, using pre-built galleries, or whatever system you use on your website.
You define export presets in the Export dialog, it's very easy, and doesn't take much time.
Enter all the settings you want for a particular preset, then click Add in the bottom left corner.
It's a standard, off-the peg design and website, but not one which accepts galleries I think as I upload individual images per page in any given gallery.