Core temperature is the CPU temperature. 46C is not a problem, 57C is a bit warm but should be OK - but 98C is a bit OTT !!
Internal temperature is presumably the motherboard sensor for the case temperature. These can vary in temperature enromously depending on where they are mounted on the motherboard (and if there are hot components near by).
One of the problems with SPEEDFAN is that you can change all the names of the sensors/fans etc. so there is little naming consistency.
You may want to try downloading a config for your motherboard. Just hit the "Info" tab and at the bottom click "Get Config" on the next page is a link to the website - click on that and answer the questions to identify your system properly. A list of user defined configs will be displayed for your motherboard - if you click on one it will give you a ticket number which you can enter in SPEEDFAN. Restart SPEEDFAN and it will be setup according to that configuration. Note that these configs are all supplied by users so cannot be guaranteed but as I understand it they all set up the program with any dangerous controls (including fan control) disabled. You may need to experiment with a number of configs to find one that is set up properly - just leave the browser window open and use BACK to go back and choose a different one.
If you genuinely seem to have temperatures above 70C regularly there is something seriously wrong. If it is a CPU temperature I would suggest you buy a new heatsink and fan for the CPU with some thermal compound (Arctic Silver is very good and comes with instructions). You might want to check temperatures in your BIOS - switch on the computer and press DEL (usually) when you see the first printed screen - go into the BIOS and look at the sensor values there - leave the system running for an hour and see if there is any significant increase in temperature.
Also a number of questions:
- What kind of graphics cards do you use - are they actively cooled by fans or passive?
- Do your PSUs have fans - are they dirty? Not easy to fix as most PSUs are sealed to stop users getting electrocuted - but a compressed air can should do the job.
- How many fans are there in your cases?
Could you take a digital photo of the inside of the worst offending system and post it here so we can see what you are looking at.