Select all the frames and then use the Align control panel. You can use the left half of the top section of the panel (Align Objects) if you want the frames to be aligned to the left or the right or perhaps have their centres aligned. Then, at the bottom of the panel in the section called “Distribute spacing”, check the “use spacing” item and make the number zero. I use millimetres so mine reads “0 mm”. Then click on the little icon showing two parallel horizontal lines between two tiny objects. Your frames should all abut each other down the page.

It is not necessary that the roman numerals actually be shown on the pages to which they apply (ie., front matter). But, unless you assign *some sort* of page number to those introductory pages, InDesign will not play ball. When you wish to assign page numbering to those pages, InDesign offers you a choice of seven different formats (at least in CS6, which is what I am using.)

You need to specify those pages by number if you wish to print them. Giving them roman numerals (or one of the other five possibilities, assuming you have used 1…2…3 for the main pages) allows you to print, for example, the Table of Contents so that you can check it against the main pages.

I’m using CS6 and later versions may not be exactly the same. But in my InDesign, the control panel across the top of the screen has a number of sections, indicated by vertical dividing lines. The tenth from the left, by my count, has five icons across the top (grouped as two and then three) and a single button on the bottom with the label “Auto Fit”. The second button from the right is the one you want. If you hover over it the little pop-up description should read “Fit frame to content”. Click on that and your image frame automatically expands or contracts (or both) to fit the image within it.

It’s worth exploring the other four buttons as well, even if all you do is read the pop-up descriptions. :-)

I’m sure there is a more elegant solution but this is what I do.

When I build my template, I make sure every paragraph has the correct style set for it. Then I change the colour of the text that will need to be edited in each incarnation of that document. I make sure the colour is an obvious contrast with the basic text so that I don’t miss any – for instance, if the basic text colour for that paragraph style is black, then I change the needing-to-be-edited text to red. BUT (this is important) I do NOT make the different coloured text a character style. That means it causes the little plus sign at the end of the name of the paragraph style in the p-styles pallet.

When I am creating a new document from the template, I go through and make the editorial changes necessary and, as I complete each paragraph, I simply click on the little second-from-the-left icon at the foot of the p-style pallet. This changes the entire paragraph back to the correct colour.

A quick visual skim through the document when I have finished the editing should show up any remaining text in the wrong colour.

Hmmm…

This sort of convinces me to stick with Yosemite and CS6 as, not being able to use ID to generate income (I am retired), the subscription model is impractical for me, yet I want to go on using ID for personal projects and I want to be able to reopen documents I have created in the past.

I wonder how long before I am forced to abandon ID (and the rest of CS) altogether? Sad.

Yes, I would like to know the answer to that as well. Because I am retired, I am unable to use my InDesign to generate income and now use it largely for producing work for my local church. So it is economically unwise for me to move to the subscription model.
However, because of this reported difficulty with El Capitan, I am still using Yosemite. How long is it going to be before I find myself cybernetically isolated and marooned?