Doing both will come off as "most natural"...

So mix it up, do some brand links to the homepage, some keyword ones, raw URLs... and also do the same for inner pages, too - most importantly, keep it natural and make sure to utilize your most powerful links for keyword links; no sense in wasting budget!

depends on keywords, for which page you optimize keywords, and if you promote particular keyword form internal page, then to ranked these keywords you have to submit your inner page in DS, or sbm.

You can build quality links to one page on your site, then piggyback off that 1st ranked page to boost additional internal pages by building internal links from the 1st ranked page to the additional internal page/s you want ranked.

Repeat...

Link flow:

deep links are called those links which are given for your inner pages whereas homepage links are those which are given to your homepages.

Good description of deep link vs home link

Both main page links and deep linking are effective for creating backlinks. What I personally feel, is that, more use of inner page linking will be more beneficial, since it looks more natural or genuine. As other members have quoted, a mix of both should be quite okay for optimization. I would personally keep the inner pages percentage greater than the homepage. Somewhat like a 60:40 ratio.

Like what was said above by MikeFriedman there's no set formula as to what distribution of links should be going to a homepage/deep pages. What looks natural is based on contextual factors and therefore there's not going to be a strict answer.

Of course there are broad/general trends that appear in most verticals...

A general rule that used to be banded around a lot was a 60/40 split between deep and home links to be optimal. This would maybe suit a typical e-commerce site.

However if you're running a large content site there should be more links to deep pages (actual content) than the homepage if you are providing valuable stuff.

If I'm to give some actionable advice I would say stay away from patterns, sprinkle your links around your site and don't only focus on your "money pages". This will provide a more sustainable return than blasting pockets of your site with concentrated pagerank.

A mix of both home page as well as the internal page links is a good and natural way of link building. Also prefer to create good internal link structure to further boost the PR and reduce the bounce rate.

Just depends on why you are getting backlinks. For instance, let's say you want to rank in Google search for a specific long tail keyword.

Unless your homepage is highly specific and targets that long tail keyword, it's not likely you will rank for it at all or at least not every high in search results.

For those situations, you would want to deep link to an inner page that is more focused on that keyword.

Your home page is going to be a 'catch all' for your main keyword. But inner pages will be the ones you use for long tail keywords that have less traffic but are more highly targeted.