Without quotes, the words in the expansion of $MY_TOKEN are passed to echo as separate arguments by the shell. The echo utility then prints each of its arguments separated by a <space> character and adds a <newline> at the end to produce a line of output.
With quotes, the shell does not perform field splitting and the quoted string is passed to echo as a single argument. And, again, the echo utility prints its argument and adds a <newline> at the end to produce a line of output.
MY_TOKEN is not define anywhere, so any output is somewhat surprising...
The first two outputs are identical, and should be - the curly braces are meant to protect a variable name and should not influence the expansion. The shell condenses multiple white spaces into single ones.
Which it doesn't if the to-be-expanded variable is enclosed in double quotes - ALL white space is retained.
Don't mix this up with single quoting which prevents shell expansion and delivers contents a AS IS.