Sorry I was a bit late to give you the details on benchmarking.
Got busy with different stuffs. Here is the code that ran on around 701407 `some-page` and `different-page` of `1158` pages. There is more types of pages, so probably the total of pages will be more.
<?php
require dirname(__DIR__) . '/index.php';
$pages = wire('pages');
$t = Debug::timer();
$items = $pages->find("template=some-page, limit=1, get_total=count");
$total = $items->getTotal();
echo "<p>Found $total some-pages in " . Debug::timer($t) . " seconds using count</p>" . PHP_EOL;
wire('pages')->uncacheAll();
// calculate total using calc method (default)
$t = Debug::timer();
$items = $pages->find("template=some-page, limit=1, get_total=calc");
$total = $items->getTotal();
echo "<p>Found $total some-pages in " . Debug::timer($t) . " seconds using calc</p>" . PHP_EOL;
wire('pages')->uncacheAll();
$t = Debug::timer();
$total = $pages->count("template=some-page");
echo "<p>Found $total some-pages using count() in " . Debug::timer($t) . " seconds using count</p>" . PHP_EOL;
wire('pages')->uncacheAll();
$t = Debug::timer();
$items = $pages->find("template=different-page, limit=1, get_total=count");
$total = $items->getTotal();
echo "<p>Found $total different-pages in " . Debug::timer($t) . " seconds using count</p>" . PHP_EOL;
wire('pages')->uncacheAll();
// calculate total using calc method (default)
$t = Debug::timer();
$items = $pages->find("template=different-page, limit=1, get_total=calc");
$total = $items->getTotal();
echo "<p>Found $total different-pages in " . Debug::timer($t) . " seconds using calc</p>" . PHP_EOL;
wire('pages')->uncacheAll();
$t = Debug::timer();
$total = $pages->count("template=different-page");
echo "<p>Found $total different-page count() in " . Debug::timer($t) . " seconds using count</p>" . PHP_EOL;
wire('pages')->uncacheAll();
$t = Debug::timer();
$first = $pages->get("template=some-page, sort=-some-page_created");
echo "<p>Found {$first->title} in " . Debug::timer($t) . " seconds</p>" . PHP_EOL;
wire('pages')->uncacheAll();
$t = Debug::timer();
$first = $pages->get("template=some-page, sort=-some-page_created, get_total=0");
echo "<p>Found {$first->title} with get_total=0 in " . Debug::timer($t) . " seconds</p>" . PHP_EOL;
wire('pages')->uncacheAll();
Result
<p>Found 701407 some-page in 2.4525 seconds using count</p>
<p>Found 701407 some-page in 2.7801 seconds using calc</p>
<p>Found 701407 some-page using count() in 2.6784 seconds using count</p>
<p>Found 1158 different-page in 0.0328 seconds using count</p>
<p>Found 1158 different-page in 0.0166 seconds using calc</p>
<p>Found 1158 source count() in 0.0028 seconds using count</p>
<p>Found some title in 3.5964 seconds</p>
<p>Found some title with get_total=0 in 0.0188 seconds</p>
Indeed the last one has shown a tremendous improvement when kept `get_total=0` .
Thank you