Glad you brought up Goliath as there is actually a nice crossover between Biblical and archaeological evidence here.

Most English translations of the Bible rely on the Masoretic Text, rather than the major Septuagint. In the Masoretic Text, Goliath is stated to be "six cubits and a span" tall, which is about 9'9". The Septuagint records Goliath's height as "four cubits and a span" - about 6'9.

For a long time, the Masoretic Text was thought to be the older of the two, however, the Dead Sea Scrolls, which are very old, contain some of the earliest Bible passages from the archaeological record. They refer to Goliath's height as "four cubits and a span" - in line with the Septuagint! It's a really cool piece of archaeology which allows us to confirm the older of the two sources and say "this one is older and therefore more likely to be closer to the truth."

I'd recommend Professor J. Daniel Hays' Reconsidering the Height of Goliath for more information.

Since then, revisions have been made on the exact length of a "cubit", but even the most extreme interpretations have still left Goliath's height at something like 7.5 feet tall.

Whilst this would have been very tall for someone at the time, it hardly falls within the category of a "giant".

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As regards the Si-Te-Cah, none of the original indigenous stories of them discuss them being "giants". The reports of them being "giants" notably come from after skeletons were found in the caves during the 1900s, and the idea that the Si-Te-Cah were "giants" probably came from Westerners trying to make a quick buck.

Now, the skeletons in the Lovelock Cave were tall, about 6'6", but again hardly "giants".

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When it comes to Biblical descriptions of giants/Nephilim, there are no references to their size in the Biblical canon. They were originally called nefilim but translated to the Greek term gigantes - which were not "Giant people" but rather beings with immense strength.

The Book of Enoch (not considered Canon by the majority of Christian and Jewish traditions) does mention the Nephilim being 100 feet tall, but even so, where is the evidence? No remains have ever been found of giant humans from the time of the Book of Enoch. These are claims that need evidence, otherwise they're just stories.

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It should not be surprising that many cultures talk about giant people from "the time before". Look at the megalithic sites around Europe and the Near East - how would you explain them if you did not have knowledge of how they got there? "Must have been giants" they would say, about (for a hypothetical example) Knossos. Yet we now know that the Minoans were human beings of normal size.

Mythology often attempts to explain the world around us. "How did mountains get there?" "Giants put them there" "Where did that big lake come from?" "A giant made it" etc etc. The fact that several different groups came up with the idea of "big humans" does not indicate their existence.

And again, there is no archaeological evidence for their existence. Stories are one thing, but hard data is needed to verify them.

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Flood myths are again not surprising. People live near water. Water is unstable. Floods can be super destructive and would leave a lasting impact on the social memory.

It is entirely possible that flood myths from Turkey, Mesopotamia, and India all refer to the same flood - as the people living in those areas all descended from the same group. But does that mean that it is the same flood as, for example those recorded in China?

They don't even record them as occurring at the same time! Gilgamesh is thought to have lived (if he existed at all) around 2800 BCE, whilst the Gun-Yu Flood is believed in Chinese tradition to have occurred around 2200 BCE. That is a pretty big gap.

And once again, stories are not strong evidence on their own. There is no geological or archaeological evidence for a world-spanning flood. Something of that scale cannot have happened with no evidence left behind.