Sizing and sharpening for the Web is only as "complicated" as you make it!
I myself take the simple approach. Almost everything is sharpened in the LR Detail panel with Making and Noise Reduction added if needed. Since this is "Input Sharpening, its only purpose is to work on the fine details of our images, and is designed to be used viewing at 100% (or using the little 100% preview in the panel.
Also, "Selective" sharpening is available through the Local Adjustment brush, and I've occasionally played with that, but it's not a "routine" of mine.
Output Sharpening is different, and can be pretty complicated, but like I say, I try to Keep It Simple. For most of my stuff I'm pretty satisfied just Exporting it from LR with the Output Sharpening set to Screen and Standard, although occasionally I've played with the High setting there.
Re-sizing for the Web is again as simple as you want it to be. I use three Export functions. To upload to my Web host I set the LR Export dialog to meet POTN limits, so 1024 at the Wide dimension although I limit the Height dimension I believe to 900 pixels. for this I don't limit the file size, and then I set the image Quality to 75. All these functions are quick in the LR Export dialog, maybe a minute for however images you want to Export.
For images that I upload directly to here, since we have a file size limit of 150 KB, well, LR has a check box for that as well, and that's the only thing you need to change in the Export dialog. Simple and quick and easy!
My third scenario is if I want to "share" an image with, for example, FaceBook. I do share photos there, both with friends, and with a couple groups that active in, a Pacific Northwest Photographers group that has about 1,300 members, and a group for photographers in the Western US states that I recently joined.
So you'll know, FaceBook has added some features, and one of those features that I enjoy is the "Full Screen View" mode. What this does when you "enter" the mode is it will "enlarge" the image from its default compressed view to, if possible, fill your screen, although it is limited to using the "original" pixels (it won't enlarge the image by creating new pixels).
So, for these shots I have chosen larger resizes, although I limit it to what I consider a pretty common screen resolution, which is 1600x1024 pixels. So the pics display larger than the "default" display, and also in this mode display with black borders around (without all the "stuff" at the side).
I'm not a Flickr user but I know that for Pro accounts they will also keep and display a larger "original" but I don't think it works quite like the FaceBook mode. FaceBook will compress the image to match your screen resolution so you are viewing the full image without having to scroll.
So, these three approaches to resizing work for me. I know that some people are very skitterish about posting pics to a public Web site, but that's a matter of personal preference, and different people will have different preferences!
As a "future" note, POTN is looking toward having a new forum software design, and once we move into that, we may be facing a different approach to resizing, so keep your eyes open!
