These two adverbial expressions are referred to as phrases that don't have good English equivalents. Although this is true, the main thing that is brushed aside is how to differentiate between them. Though they are different enough to the point that that shouldn't really be an issue, it's best to make sure that you know when to use them.
やはり, also やっぱり, やっぱし, and やっぱ in slang, means "just as one thought", "as of/still yet/now". It may also suggest a feeling of returning back to one's original idea or motives.
This here is weird as I thought.
This is the house just as I had imagined.
I knew that he was killed.
It's bad in the end.
Here you come again.
"How was your summer break?". "I studied Japanese". "Well, so you got to do a lot of studying, right?". "Yes, but, I thought that there was a lot of free time". "True, by the way, what kind of restaurant did you go to yesterday?". "I went to a Mexican food restaurant". "Was it good?". "Yes, but since I'm Korean, I thought that the flavor was quite different from a Korean restaurant".
さすが is just one of those words that gives a lot of trouble because it doesn't have an English equivalent. さすが shows something good is as expected. It can also be used with the negative to show that although one thought one's expectations would come through, things don't pan out so. This pattern is often used with ～だけあって.
Just as expected.
It is indeed said that time is money.
Grammar Note: とは quotes a set phrase. In this set phrase, なり is simply a classical copular verb.
It's just like her to.
Since Tanaka is a pro, he can hit home runs as expected.
Given that it's a famous restaurant, even when you get a reservation, there is always a line of customers, and it takes a long time to get seated.
He is worthy to be the president.
Even I can't say to that extent.
Variant Note: さすがの ＝ さしもの. However, the latter is rare and is seen in literature.
Orthography Note: さすが can be seldom seen written in 漢字 as 流石.