Q: Does landing page load time effect Quality Score?
A: Yes, the load time of your landing pages and site in general is a factor in your AdWords Quality Score , albeit not the most important factor. Google takes load times into account because they have a significant effect on user experience. To reduce your load times, try optimizing your images and CSS and doing away with unnecessary animation, such as moving ads.
Q: You said that CPC bid does not affect Quality Score. But a higher ad may have a higher CTR, so does it indirectly affect QS?
A: Google normalizes your click-through rate based on your ad position. Your expected CTR  is higher if your ad is in the top position, so your CTR is only compared to other ads in the same position. It's sort of like being graded on a curve. So no, bidding up to a higher position to improve your CTR will not consequently improve your Quality Score.
Q: If a keyword has a low number of searches, do I have to pause this keyword to improve CTR and consequently improve my Quality Score?
Low-volume keywords  don't necessarily have low Quality Scores. Your Quality Score is based in large part on your click-through rate (the ratio of clicks to impressions), not your total number of clicks. Even if your keyword has a low monthly search volume, your ad could have a stellar CTR and therefore a good Quality Score. If your CTR and Quality Score for a low-volume keyword are low, make sure that your ad and landing page are actually relevant to the keyword. Also test different versions of your ad text.
Q: From a Quality Score perspective, would it make sense to separate Search campaigns from Content Network campaigns? The Content CTR is obviously lower than the Search CTR; I am concerned that the Content CTR would negatively affect the Search CTR of the keywords in the same campaign.
A: Quality Score is calculated separately for each network. Your CTR on the Content Network will have no effect on your Search Network Quality Score. However, the best practices for optimizing your ad groups on each network are different. On the search network, you’ll generally want to be more specific. On the content network, Google might have trouble matching you to good sites if you use a very specific list of keywords. So, yes, you should always have separate Search and Content campaigns.
Q: What is modified broad match?
A: Modified broad match is a newer matching option that is more restrictive than regular broad match but still less restrictive than phrase or exact match. To use modified broad match, place a plus sign before any words in your keyword phrase that should appear in any search query that triggers your ad, either exactly or in close variation. For example, if your keyword is [+detangling spray], your ad will only display in response to queries that include "detangling" or close variations like "detangler," but Google may display it in response to queries that include synonyms or more distantly related versions of "spray." (Learn more about modified broad match here .)
Modified broad match can help you optimize your budget, but remember that changing your match type won't affect your Quality Score.